Antibody Identification

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What does LISS do?

increases the chance that an antibody will bind to its corresponding antigen. Decreasing the ionic strength of the solution in which the red cells are suspended reduces the positive ion cloud that normally surrounds negatively-charged red cells. (Decreases Zeta Potential) This allows an antibody (which is positively charged) to approach its target antigen more readily.

warm-reacting autoantibody

reactivity in the AHG phase, suggesting a warm-reacting antibody (probably IgG class) reactivity in all 3 screening cells strong (3+) reactivity in all screening cells positive autocontrol

Monospecific AHG reagents

reagents prepared by separating the specificities of the polyspecific AHG reagents into individual sources of anti-IgG and anti-C3d/anti-C3b

Why do IgM antibodies, such as those formed against the ABO antigens, have the ability to directly agglutinate red blood cells (RBCs) and cause visible agglutination? A) IgM antibodies are larger molecules and have the ability to bind more antigen B) IgM antibodies tend to clump together more readily to bind more antigen C) IgM antibodies are found in greater concentrations than IgG antibodies D) IgM antibodies are not limited by subclass specificity

A) IgM antibodies are larger molecules and have the ability to bind more antigen An IgM molecule has the potential to bind up to 10 antigens, as compared to a molecule of IgG, which can bind only two.

Autoantibodies demonstrating blood group specificity in Warm Autoimmune Hemolytic anemia are associated more often with which blood group system? A) Rh B) I C) P D) Duffy

A) Rh Warm autoantibodies often exhibit Rh specficity. [Harmening 2012, p454]

What is the increase in the risk percentage for developing antibodies against red cell antigens (RBC alloimmunization) for patients who are characterized as chronically transfused patients? A) 1% - 4% B) 2% - 8% C) 5% - 10% D) 20% - 50%

B) 2% - 8% In chronically transfused patients, the risk for them developing antibodies against red cell antigens (RBC alloimmunization) increases by 2% - 8%.

Which of the following blood group antibodies will no longer react with its respective antigens once those antigens are treated with proteolytic enzymes? A) anti-C B) anti-K C) anti-Fya D) anti-Jka

C) anti-Fya The Fya, Fyb, M, N, and S antigens are destroyed when red cells are treated with proteolytic enzymes. [Harmening 2012, p69]

What immunoglobulin class is primarily associated with ABO antibodies? A) IgA B) IgG C) IgE D) IgM

In which of the following is the indirect antiglobulin test utilized? A) reverse ABO testing B) immediate spin crossmatch C) C antigen testing D) antibody detection (screening) test

D) antibody detection (screening) test following incubation at 37C, antibody screening (detection) tests must include an indirect antiglobulin phase to facilitate detection of clinically significant antibodies. [Harmening 2012, p 109]

What happens if the antibody screen is positive?

Further identification of the specificity of any antibody detected (using panels of red cells of known antigenicity)makes it possible to test donor blood for the absence of the corresponding antigen. Primary response to first antigen exposure requires 20-120 days;antibody is largely IgM with a small quantity of IgG. Secondary response requires 1-14 days;

When are IgM antibodies detected?

Immediate Spin

Fill in The Blank Mixed field reactions are expected with these: Lutheran, ______, A3 (and post bone marrow transplant)

Sid

Is anti-Di^b implicated in HDFN?

Yup

In a cold autoadsorption procedure, pretreatment of the patient's red cells with which of the following reagents is helpful? A) ficin B) phosphate-buffered saline at pH 9.0 C) low ionic strength saline (LISS) D) albumin

a) ficin Treating autologous cells with a proteolytic enzyme such as ficin enhances the adsoprtion of the cold reactive antibody. [AABB Tech Manual 2017, p 399]

Antibody titer

refers to the amount of antibody present in the person's plasma.

Likelihood of finding compatible blood

The likelihood of antigen NEGative blood = 100X(Antigen frequency) Example: If patient has an anti-Jka (Antigen Frequency in US donor population ~ 75%), then the likelihood of finding an antigen negative unit is 100%-75%, or ~25%. Thus if the laboratorian needs to find 1 antigen negative unit, one should test 4 units.

AHG phase

is anti-IgG; it will bind the Fc portion of the bound IgG antibodies with its own Fab portions. This will now allow the reactivity in the tube to be seen as agglutination by the human eye

What sample is best for detecting complement-dependent antibodies? A) Plasma stored at 4C for no longer than 24 hours B) Serum stored at 4C for no longer than 48 hours C) Either serum or plasma stored at 20C-24C no longer than 6 hours D) Serum heated at 56C for 30 minutes

B) Serum stored at 4C for no longer than 48 hours Serum stored at 4C for no longer than 48 hours preserves complement activity. Plasma is inappropriate because most anticoagulants chelate calcium needed for activation of complement. Heating the serum to 56C destroys complement.

Paroxysmal Cold Hemoglobinuria (PCH):

1) Acquired Disease ---Idiopathic or associated with syphilis 2) IgG cold antibody with bithermal activity ---Donath-Landsteiner antibody (a) Antibody is directed against the P blood group antigen (b) At cold temperatures -----binds to RBCs and fixes complement (c) At 37C -----Detaches from RBCs and activates complement causing intravascular hemolysis 3) Hemolytic anemia occurs when moving from a cold to warm environment

What are the antibodies that commonly produce intravascular hemolysis?

ABO Kidd P (paroxysmal cold hemoglobinuria)

When are IgG antibodies detected?

AHG

If all Red Cells are reactive at similar strengths and phases what do you suspect?

An Antibody to a high incidence antigen OR multiple antibodies

What are the 4 most common antibodies implicated in immediate HTR?

Anti-A Anti-Kell Anti-Jk^a Anti-Fy^a

What are the four most common antibodies implicated in HDFN?

Anti-AB Anti-D Anti-Kell Anti-c

What are the antibodies that react at room temperature?

Anti-M Anti-N Anti-P1 Le^a Le^b

What is an Autoantibody?

Antibody to an antigen an individual possesses

A woman who is 24 weeks pregnant has a positive antibody screen. You should: A) Run a panel to identify the antibody; titer if necessary B) Do nothing until 30 weeks of pregnancy C) Administer RhIg (Rh immune globulin) prophylactically D) Absorb the antibody onto antigen-positive cells

Which of the following best describes MN antigens and antibodies? A) Well developed at birth, susceptible to enzymes, generally saline-reactive B) Not well-developed at birth, susceptible to enzymes, generally saline-reactive C) Well-developed at birth, not susceptible to enzymes, generally saline reactive D) Well developed at birth, susceptible to enzymes, generally antiglobulin-reactive

An antibody shows strong reactions in all test phases. All screen and panel cells are positive. The serum is then tested with a cord cell and the reaction is negative. What antibody is suspected? A) Anti-I B) Anti-i C) Anti-H D) Anti-p

A) Anti-I Adult cells contain mostly I antigen, and anti-I would react with all adult cells found on screen or panel cells. Cord cells, however, contain mostly i antigen and would test negative or only weakly positive with anti-I.

A patient is admitted to the hospital. Medical records indicate that the patient has a history of anti-Jk^a. When you performed the type and screen, the type was O positive and screen was negative. You should: A) Crossmatch using units negative for Jk^a antigen B) Crossmatch random units, since the antibody is not demonstrating C) Request a new sample D) Repeat the screen with enzyme-treated screening cells

A) Crossmatch using units negative for Jk^a antigen The Kidd antibodies are notorious for disappearing from serum, yielding a negative result for the antibody screen. If a patient has a history of a Kidd antibody, blood must be crossmatched using antigen-negative units. If the patient is transfused with the corresponding antigen, an anamnestic response may occur with a subsequent hemolytic transfusion reaction.

AUTOantibodies demonstrating blood group specificity in Warm Autoimmune Hemolytic Anemia are associated more often with which blood group system? A) Rh B) I C) P D) Duffy

A) Rh Warm autoantibodies often exhibit Rh specificity. [Harmening 2012, p454]

A patient is suspected of having paroxysmal cold hemoglobinuria (PCH). Which pattern of reactivity is characteristic of the Donath-Landsteiner antibody, which causes this condition? A) The antibody attaches to RBCs at 4C and causes hemolysis at 37C B) The antibody attaches to RBCs at 37C and causes agglutination at the IAT phase C) The antibody attaches to RBCs at 22C and causes hemolysis at 37C D) The antibody attaches to RBCs and causes agglutination at the IAT phase

A) The antibody attaches to RBCs at 4C and causes hemolysis at 37C The Donath-Landsteiner antibody has anti-P specificity with biphasic activity. The antibody attaches to RBCs at 4C and then causes the red cells to hemolyze when warmed to 37C.

Which of the following antibodies in the Lutheran system is most likely to be IgM and detected as a direct agglutinin? A) anti-Lu^a B) anti-Lu^b C) anti-Lu3 D) anti-Au^a

A) anti-Lu^a Most examples of anti-Lu^a agglutinate saline suspended cells. Most examples of other Lutheran antibodies are IgG and react at 37C by IAT. [AABB Tech Manual 2017, p327]

A patient has received 4 units of blood 2 years previously and now has multiple antibodies. He has not been transfused sicne that time. It would be most helpful to: A) phenotype his scells to determine which additional alloantibodies may be produced B) recommend the use of directed donors, which are more likely to be compatible C) use proteolytic enzymes to destroy "in vitro" acitivity of some of the antibodies D) freeze the patient's serum to use for antigen typing of compatible units

A) phenotype his cells to determine which additional alloantibodies may be produced Determining the patient's phenotype allows focusing identification procedures toward antibodies the patient can develop [AABB Tech Manual 2017, p355]

The antibodies of the Kidd blood group system: A) react best by the indirect antiglobulin test B) are predominantly IgM C) often cause allergic transfusion reactions D) do not generally react with antigen positive, enzyme treated RBCs

A) react best by the indirect antiglobulin test Antibodies in the Kidd blood group system are IgG and react best at the antiglobulin phase. These antibodies are associated with delayed hemolytic transfusion reactions and reactivity can be enhanced by testing with enzyme pretreated cells. [Harmening 2012, p198]

What antibodies could an R1R1 make if exposed to R2R2 blood? A) Anti-e and anti-C B) Anti-E and anti-c C) Anti-E and anti-C D) Anti-e and anti-c

B) Anti-E and anti-c The R1R1 (DCe/DCe) individual does not have the E or c antigen and could make anti-E and anti-c antibodies when exposed to R2R2 (DcE/DcE) cells.

Which antibody is frequently seen in patients with Warm Autoimmune Hemolytic anemia? A) Anti-Jk^a B) Anti-e C) Anti-K D) Anti-Fy^b

B) Anti-e Anti-e is frequently implicated in cases of warm autoimmune hemolytic anemia. The corresponding antigen is characterized as high frequency in the Rh system and can mask the presence of other alloantibodies.

A major crossmatch and screening cells are 2+ at IS, 1+ at 37C, and NEGative at the IAT phase. Identify the most likely problem: A) Combination of antibodies B) Cold alloantibody C) Rouleaux D) Test error

B) Cold alloantibody The reaction pattern fits that of a cold antibody reacting at the IS phase and of sufficient titer to persist at 37C incubation. The reactions disappear in the IAT phase.

Which of the following statements is true concerning the MN genotype? A) Antigens are destroyed using bleach-treated cells B) Dosage effect may be seen for both M and N antigens C) Both M and N antigens are impossible to detect because of cross-interference D) MN is a rare phenotype seldom found in routine antigen typing

B) Dosage effect may be seen for both M and N antigens Dosage effect is the term used to describe the phenomenon of an antibody that reacts more strongly with homozygous cells than with heterozygous cells. Dosage effect is a characteristic of the genotype MN because the M and N antigens are both present on the same cell. This causes a weaker reaction than seen with RBCs of either the MM or NN genotype, which carry a greater amount of the corresponding antigen.

The k (Cellano) antigen is a high-frequency antigen and is found on most red cells. How often would one expect to find the corresponding antibody? A) Often, because it is a high frequency antibody B) Rarely, because most individuals have the antigen and therefore would not develop the antibody C) It depends upon the population, because certain racial and ethnic groups show a higher frequency of anti-k D) Impossible to determine without consulting regional blood group antigen charts

B) Rarely, because most individuals have the antigen and therefore would not develop the antibody The k antigen is found with a frequency of 99.8%; therefore, the k-negative person is rare. Because k-negative individuals are very rare, the occurrence of anti-k is also rare.

Which procedure would help to distinguish between an anti-e and anti-Fy^a in an antibody mixture? A) Lower the pH of test serum B) Run an enzyme panel C) Use a thiol reagent D) Run a LISS panel

B) Run an enzyme panel Enzyme-treated cells will NOT react with Duffy antibodies. Rh antibodies react more strongly with enzyme-treated red cells. An enzyme panel, therefore, would enhance reactivity of anti-e and destroy reactivity to anti-Fy^a.

Antibodies from which of the following blood group systems are notorious for causing delayed hemolytic transfusion reactions? A) Rh B) Kell C) Duffy D) Kidd

D) Kidd Anti-Jk^a and anti-Jk^b are often weakly reactive and often drop to undetectable levels in the serum. [AABB Tech Manual 2017, p333]

When may an IS crossmatch be performed? A) When a patient is being massively transfused B) When there is no history of antibodies and the current antibody screen is negative C) When blood is being emergency released D) When a patient has not been transfused in the past 3 months

B) When there is no history of antibodies and the current antibody screen is negative The IS crossmatch may be performed when the patient has no history of antibodies and the current antibody screen is negative.

HLA antibodies are: A) naturally occuring B) induced by multiple transfusions C) directed against granulocyte antigen only D) frequently cause hemolytic transfusion reactions.

B) induced by multiple transfusions HLA antibodies are formed in response to pregnancy, transfusion, or transplantation and are therefore not naturally occuring. They are associated with febrile nonhemolytic transfusion reactions and TRALI. They are directed against antigens found on granulocytes and other cells such as platelets. [AABB Tech Manual 2017, p447]

Proteolytic enzymes originate from plants

Ficin comes from Figs BromeLin comes from pineappLe papain comes from papaya

Which of the following antibodies characteristically gives a refractile mixed-field appearance? A) Anti-K B) Anti-Di^a C) Anti-Sd^a D) Anti-s

C) Anti-Sd^a Anti-Sd^a characteristically gives a refractile mixed-field agglutination reaction in the IAT phase. The refractile characteristic is more evident under the microscope.

A 56-year-old female with cold agglutinin disease has a positive direct antiglobulin test (DAT). When the DAT is repeated using monospecific antiglobulin sera, which of the following is most likely to be detected? A) IgM B) IgG C) C3d D) C4a

C) C3d Cold agglutinin disease is associated with cold reactive antibodies that typically activate complement. Cells that do not undergo lysis due to complement activation have C3d attached to the RBCs. [AABB Technical Manual 2017, p398]

A technologist performs an antibody study and finds 1+ and weak positive reactions for several of the panel cells. The reactions do not fit a pattern. Several selected panels and a patient phenotype do not reveal any additional information. The serum is diluted and retested, but the same reactions persist. What type of antibody may be causing these results? A) Antibody to a high-frequency antigen B) Antibody to a low-frequency antigen C) High titer low avidity (HTLA) D) Anti-HLA

C) High titer low avidity (HTLA) HTLA antibodies may persist in reaction strength, even when diluted. These antibodies are directed against high-frequency antigens (such as Ch^a). They are not clinically significant buth, when present, are responsible for a high incidence of incompatible crossmatches.

Cold agglutinin disease is associated with an antibody specificity toward which of the following? A) Fy:3 B) P C) I D) Rh:1

C) I Anti-I is associated with cold agglutinin disease. [AABB Tech Manual 2017, p399]

The purpose of the direct antiglobulin test is to detect: A: In vitro sensitization of RBCs by IgM antibodies B: In vivo sensitization of RBCs by complement and IgM antibodies C: In vitro sensitization of RBCs by IgG, IgM, and complement D: In vivo sensitization of RBCs by IgG antibody

A patient showed positive results with screening cells and 4 donor units. The patient autocontrol was negative. What is the most likely antibody? A) Anti-H B) Anti-S C) Anti-Kp^a D) Anti-k

D) Anti-k Anti-k (cellano) is a high-frequency alloantibody that would react with screening cells and most donor units. The negative autocontrol rules out autoantibodies. Anti-H and anti-S are cold antibodies and anti-Kp^a is a low frequency alloantibody.

All of the following are reasons for performing an adsorption, EXCEPT: A) Separation of mixtures of antibodies B) Removal of interfering substances C) Confirmation of weak antigens on red cells D) Identification of antibodies causing a positive DAT

D) Identification of antibodies causing a positive DAT Antibodies causing a positive DAT would be coating red cells and would require an elution, not an adsorption, to identify them.

The purpose of adding antibody coated (Coombs control) cells to all negative AHG tubes is to: A:Ensure proper cell washing and addition of AHG reagent B:Ensure proper tube reading C:Check for hemolysis or reaction of complement D:Check for attachment of additional antibody

What does a NEGative antibody screen mean?

A negative antibody screen implies that a recipient can receive type-specific (ABO-Rh identical) blood with minimal risk

Immune A and B alloantibodies differ from non-red cell stimulated (naturally occurring) A and B alloantibodies in that the immune antibodies: A) Are generally IgG rather than IgM B) Are unable to cross the placenta C) Can be enhanced in reactivity by incubation at 4oC D) Cause direct agglutination at room temperature E) Rarely cause clinical hemolysis

A) Are generally IgG rather than IgM This question isn't really about ABO so much as it's about characteristics of IgG and IgM antibodies in blood banking. In short, naturally occurring antibodies are generally of the IgM class, not able to cross the placenta, enhanced in reactivity by incubation at 4C, and can cause direct agglutination at room temperature. These antibodies, aside from the ABO blood group, are not usually capable of causing clinical hemolysis. IgG antibodies are typically what you ultimately get from red-cell stimulated antibody formation, and they can cross the placenta and are not very reactive (if at all) at 4C and room temperature. They "like" the AHG phase of testing and 37C, and generally are more likely to cause clinical hemolysis.

Which characteristics are true of all three of the following antibodiesl: anti-Fy^a, anti-Jk^a, and anti-K ? A) Detected at the IAT phase; may cause hemolytic disease of the newborn and hemolytic transfusion reactions B) Not detected with enzyme-treated cells C) Requires the IAT technique for detection; usually not associated with HDFN D) Enhanced reactivity with enzyme-treated cells; may cause severe hemolytic transfusion reactions

A) Detected at the IAT phase; may cause hemolytic disease of the newborn and hemolytic transfusion reactions Anti-Fy^a, anti-Jk^a, and anti-K are usually detected at IAT and all may cause HDN and transfusion reactions that may be hemolytic. Reactivity with anti-Fy^a is lost with enzyme-treated red cells, but reactivity with anti-Jk^a is enhanced with enzyme-treated cells. Reactivity with anti-K is unaffected by enzyme-treated cells.

An antibody that causes In Vitro hemolysis and reacts with the red cells of 3 out of 10 AHG-crossmatched donor units is most likely: A) anti-Le^a B) anti-s C) anti-k D) anti-E

A) anti-Le^a Lewis antibodies may bind complement and fresh serum that contains anti-Le^a may hemolyze Le(a+) red cells in vitro. Approximately 22% of the population is Le(a+). [Harmening 2012, p 178]

Which antibody would not be detected by group O screening cells? A) Anti-N B) Anti-A1 C) Anti-Di^a D) Anti-k

B) Anti-A1 ABO antibodies are not detected by group O screening cells, because O cells contain no A or B antigens.

What is the approximate probability of finding compatible blood among random Rh-positive units for a patient who has anti-c and anti-K? (Consider that 20% of Rh-positive donors lack c and 90% lack K) A) 1% B) 10% C) 18% D) 45%

C) 18% Multiplication of the individual compatibility frequencies results in the percentage of compatible donors that would lack both antigens. 0.20 X 0.90= 0.18 or 18% [Harmening 2012, p 232]

A patient demonstrates 4+ reactivity with all red cells tested and the autocontrol is nonreactive. This high incidence antibody was suspected to be related to the P1PK blood group system as the patient is the rare p phenotype. What antibody specificity should be suspected? A) anti-IP1 B) anti-P2 C) anti-PP1P^k D) anti-P1

C) anti-PP1P^k Anti-PP1P^k is the high incidence antibody made by individuals with the p phenotype. This antibody has an association with early spontaneous abortion. [AABB Tech Manual 2017, p290]

Which adsorption technique removes cold (IgM) antibodies, particularly anti-I specificities? A) Cold autoadsorption B) Warm autoadsorption C) Differential (allogeneic) D) Rabbit erythrocyte stroma (RESt)

D) Rabbit erythrocyte stroma (RESt) RESt removes cold (IgM) antibodies, particularly anti-I specificities. However, it may adsorb anti-B and other IgM antibodies. Cold autoadsorption uses patient red cells to remove cold autoantibodies to determine whether alloantibodies are present. Warm autoadsorption uses patient red cells are used to remove warm autoantibodies to determine whether alloantibodies are present. Allogeneic adsorption uses known phenotyped red cells to separate specificities: 1) warm autoantibodies from alloantibodies 2) alloantibodies with several specificities.

Fill in the Blank Anti-______ antibody is produced by all Gerbich antigen-NEGative phenotypes

Ge2

What does an antibody screen detect?

Detects antibodies to non-ABO redblood cell antigens in recipient's serum or plasma, using reagent red cells selected to possess antigens against which common antibodies can be produced.

A 25-year-old man presents with fever, nonproductive cough, and fatigue. Physical examination reveals no signs of consolidation the lungs; however, a chest x-ray shows an interstitial type of pneumonia. A CBC reveals a hemoglobin of 7 g/dL and a normal MCV, WBC, and platelet. -The peripheral smear shows clumping of RBCs. -The corrected reticulocyte count is increased. -The direct Coombs test is positive. An indirect Coombs test is positive for an antibody with I antigen specificity. -A dipstick of urine is positive for blood; however, the urine sediment does not contain RBCs. What is the most likely diagnosis? A) WAIHA B) Sickle Cell Anemia C) NonMegaloblastic Crisis D) Anemia of Chronic Disease E) Autoimmune Hemolytic Anemia-Cold

E) Autoimmune Hemolytic Anemia-Cold The patient has Mycoplasma pneumoniae atypical pneumonia complicated by a cold (IgM) type of autoimmune hemolytic anemia due to anti-I antibodies. IgM antibodies (cold agglutinins) cause clumping of RBCs in the peripheral blood. The direct Coombs test is positive, because C3b is coding the cells (IgM falls off the cells at warm temperatures). The patient has an intravascular hemolytic anemia (hemoglobinuria), the latter due to complete activation of the complement system.

What antibody class is typically involved in Extravascular hemolysis?

IgG

What is PCH?

IgG cold antibody with bithermal activity; Intravascular Hemolysis

Fill in the Blank IgG subclasses 1, 2, and 3 can activate complement, while ________ typically does not have this ability

IgG4

When are antibody screens positive?

In the Presence of alloantibody OR autoantibodies.

Coombs test

The test detects IgG or complement coating a patient's cells in vivo. A positive test may indicate the presence of immune-mediated destruction of red cells within the patient. Typically, a polyspecific reagent is initially used. This reagent will detect either complement or IgG coating the cells. If this reaction is positive for agglutination, monospecific reagents will then be used to determine if IgG, complement, or both are coating the cells

The screening cells are always what group?

group O

Likelihood of finding compatible blood (multiple antibodies)

When blood is needed for a patient with two or more alloantibodies the frequencies of antigen negative blood in the population are multiplied. Example: if the patient has anti-Jka (Antigen frequency in US donor population~75%) and Anti-E( Antigen frequency in US donor population ~30%)... Likelihood of Jka antigen NEGative = 100%-75% =25%=0.25 Likelihood of E antigen NEGative = 100%-70% = 30% = 0.3 Then the frequency of Jka and E negative blood is 0.25 X 0.3 = 0.075 X 100% = 7.5% 1 / (7.5 X 100) = ~13 ~13 units have to be crossmatched to find one compatible pRBC unit.

What is Neutralization?

an antibody identification technique that combines a soluble antigen with antibody in vitro. If the patient's serum contains the antibody, the soluble antigen makes the antibody inactive.

Fill in The Blank Unexpected ______________ are found in the sera of 0.3 to 3% of donor and patient populations. Many ______________ are of clinical importance since they may cause decreased red blood cell survival as the result of hemolytic transfusion reactions, hemolytic disease of the newborn or autoimmune hemolytic anemia. In vitro antibody detection (screening) tests are employed to reveal the presence of these antibodies in patient and donor sera. Source (Immucor Package Insert Rev 07/19)

antibodies

Polyspecific AHG reagent

contains both anti-IgG and anti-C3d antibodies and detects both IgG and C3d molecules on red cells

Anti-I in cold agglutinin disease may cause a positive direct antiglobulin test (DAT) because of: A) anti-I agglutinating the cells B) C3d bound to the red cells C) T-activation D) C3c remaining on the red cells after cleavage of C3b

B) C3d bound to the red cells In cold agglutinin syndrome, anti-I acts as a complement binding antibody with a high titer and high thermal amplitude. The complement cascade is activated and C3d remains on the red cell membrane of circulating cells.

Screening cells and major crossmatch are positive on IS only, and the autocontrol is negative. Identify the problem. A) Cold alloantibody B) Cold autoantibody C) Abnormal protein D) Antibody mixture

A) Cold alloantibody A cold alloantibody would show a reaction with screening cells and donor units only at IS phase. The negative autocontrol rules out autoantibodies and abnormal protein.

What is an elution?

procedure that dissociates antigen-antibody complexes on red cells; freed IgG antibody is tested for specificity

What is an Adsorption?

procedure that uses red cells (known antigens) to remove red cell antibodies from a solution (plasma or antisera); group A red cells can remove anti-A from solution

An antibody screen performed using solid phase technology revealed a diffuse layer of RBC's on the bottom of the well. these results indicate: A) a positive reaction B) a negative reaction C) serum was not added D) red cells have a positive DAT

A) a positive reaction In the solid phase technology, the antibody screening cells are bound to the surface of the well. Antibody specific for antigen on the red blood cells attaches, resulting in a diffuse pattern of RBCs in the well. A NEGative reaction would have manifested as a pellet of RBCs in the bottom of the well. [Harmening 2012, p279]

Which of the following are true of all 3 of the following antibodies: anti-Fy^a, anti-Jk^a, and anti-K? A) detected at IAT phase and may cause hemolytic disease of the fetus and newborn (HDFN) and transfusion reacitons B) not detected with enzyme treated cells; may cause delayed transfusion reactions C) requires the IAT technique for detection; usually not responsible for causing HDFN D) may show dosage effect; may cause severe hemolytic transfusion reactions

A) detected at IAT phase and may cause hemolytic disease of the fetus and newborn (HDFN) and transfusion reacitons All 3 antibodies can cause HDFN and delayed transfusion reactions. Anti-Jk^a is associated with showing dosage. [Harmening 2012, p210-212]

An antibody screen demonstrates a mixed field agglutination pattern. To which blood group system will this antibody most likely belong? A) Lewis B) Lutheran C) Kell D) Kidd

B) Lutheran Lutheran antibodies, particularly Anti-Lu^a typically demonstrate a mixed field pattern of reactivity. Lewis antibodies do NOT show dosage or mixed field agglutination Kell antibodies typically react very strongly, 3+ or 4+. They do NOT demonstrate a mixed field pattern Though Kidd antibodies may demonstrate a 1+ or 2+ reaction strength, they do NOT demonstrate a mixed field pattern of reactivity.

A technologist is having great difficulty resolving an antibody mixture. One of the antibodies is anti-Le^a. This antibody is not clinically significant in this situation, but it needs to be removed to reveal the possible presence of an underlying antibody of clinical significance. What can be done? A) Perform an enzyme panel B) Neutralize the serum with saliva C) Neutralize the serum with hydatid cyst fluid D) Use DTT (dithiothreitol) to treat the panel cells

B) Neutralize the serum with saliva Saliva from an individual with the Le gene contains the Le^a antigen. This combines with anti-Le^a, neutralizing the antibody. Panel cells treated with DTT (0.2M) lose reactivity with anti-K and other antibodies, but not anti-Le^a. Hydatid cyst fluid neutralizes anti-P1.

What does the 3+3 rule ascertain? A) An antibody is ruled in B) An antibody is ruled out C) 95% confidence that the correct antibody has been identified D) 95% confidence that the correct antibody has not been identified

C) 95% confidence that the correct antibody has been identified The 3+3 rule ascertains correct identification of antibody at a confidence level of 95%. For this level to be met, reagent red cells are found containing target antigen to suspected antibody that react in test phase; likewise, reagent red cells devoid of antigen will not react in test phase.

If detected in antibody screen testing, which of the following antibodies is NOT considered clinically significant in prenatal patients? A) Anti-M B) Anti-N C) Anti-Leb D) Anti-Fya

C) Anti-Leb Anti-Leb may be detected in antibody screen testing of prenatal patients; however, this antibody is considered clinically insignificant. It is not indicated in causing hemolytic disease of the fetus and newborn (HDFN). Although rarely seen, both anti-M and anti-N can potentially cause mild to moderate HDFN. The most common clinically significant antibodies noted in prenatal patients includes the following: anti-Fya, anti-K, anti-D, anti-E, anti-e, anti-C, and anti-c. These IgG antibodies have been determined to cause moderate to severe HDFN.

Bombay phenotype (Oh) individuals may have antibodies with all the following specificities EXCEPT: A) Anti-A B) Anti-B C) Anti-H D) Anti-O E) Anti-A,B

D) Anti-O The ubiquitous presence of questions about Bombay phenotypes on standard exams would incorrectly lead you to assume that the Bombay phenotype is quite common. This couldn't be farther from the truth, as Bombay is spectacularly rare! Whether you ever actually see a case, you will likely need to answer a question about Bombay on a standard exam. For this question, you must recall that the Bombay phenotype and the Bombay genotype (hh), mean that an individual is missing the H structure both on RBCs as well as in plasma and secretions (the Bombay person is a non-secretor, or sese). Since an intact H structure is a prerequisite for addition of the A and B antigens, you will then be able to deduce that the following antibodies can be present in the serum of a Bombay individual simply because you know the corresponding antigen is missing: anti-A, anti-B, anti-A,B, and anti-H. O, of course, is not an antigen, it's the lack of A and B antigens, so anti-O is not a legitimate antibody.

In which of the following is the indirect antiglobulin test utilized? A) reverse ABO testing B) immediate spin crosmmatch C) antigen testing D) antibody detection (screening) test

D) antibody detection (screening) test Following incubation at 37C, antibody screening (detection) tests must include an indirect antiglobulin phase to facilitate detection of clinically significant antibodies. [Harmening 2012, p 109]

The process of separation of antibody from its antigen is known as: A) diffusion B) adsorption C) neutralization D) elution

D) elution An elution is the process of removal of antibody from red blood cells. The product of the elution method is an eluate. The eluate contains the antibody and can be used in antibody identification methods. [Harmening 2012, p454]

List the antigens that are associated with displaying DOSAGE:

MNS Kidd C/c E/e Duffy

In a cold autoadsorption procedure, pretreatment of the patient's red cells with which of the following reagents is helpful? A) ficin B) phosphate buffered saline at a pH of 9.0 C) low ionic strength saline (LISS) D) albumin

A) ficin Treating autologous cells with a proteolytic enzyme such as ficin enhances the adsorption of the cold reactive antibody

A patient recieved 4 units of blood 2 years previously and now has multiple antibodies. He has not been transfused since that time. It would be most helpful to: A) phenotype his cells to determine which additional alloantibodies may be produced B) recommend the use of directed donors, which are more likely to be compatible C) use proteolytic enzymes to destroy the "in vitro" activity of some of the antibodies D) freeze the patient's serum to use for antigen typing of compatible units

. Which of the following is the best explanation for why the ABO system is the most important blood group system in transfusion safety? A) It is the only system in which antibodies are normally produced for the antigens an individual lacks B) ABO antibodies are capable of causing rapid, severe intravascular hemolysis C) Reactions with ABO antibodies are the most common cause of transfusion-related death D) ABO antibodies are often implicated in severe hemolytic disease of the fetus and newborn E) Routine ABO forward and reverse grouping is difficult to interpret and fraught with error

B) ABO antibodies are capable of causing rapid, severe intravascular hemolysis B is the best answer because of the potential horrific, near-immediate consequences of receiving ABO-mismatched blood. While ABO is famous for the reciprocal antibodies, it is not the only blood group with "naturally occurring" antibodies. Transfusion-related acute lung injury (TRALI) is currently the most common cause of transfusion-related death (though hemolytic transfusion reactions are second). Answer D is incorrect because the HDFN caused by ABO antibodies (almost always in group O moms) is generally mild (and some don't even refer to it as "HDFN"; see BBGuy.org/038). Answer E is a subjective statement; only a minority of samples submitted for ABO typing would have discrepancies that cause difficult in interpretation (and blood banks do a darn good job even with those!). (BB Guy)

An O positive patient has no reactions at immediate spin but both screen cells are positive and all antibody panel cells are reacting 1+ at AHG. The auto control is 1+. What would you suspect to be the cause? A) Cold autoantibody B) Warm autoantibody C)Anti-Lea D) Anti-K

B) Warm autoantibody There is no reaction at the immediate spin phase so the cold autoantibody can be eliminated. Reactivity is occurring at AHG with all panel cells and the auto control is positive which can indicate a warm autoantibody. Adsorption and elution techniques may be beneficial to determine if other clinically significant antibodies are present or to help identify the warm autoantibody. Reactions due to anti-Le^a would likely be at the immediate spin phase, and would not occur on all panel cells. Reactions due to anti-K would likely occur at AHG, but would not occur on all panel cells.

The following results were obtained in pretransfusion testing: 37C SCI: 0 SCII: 0 AC: 0 IAT SCI : 3+ SCII: 3+ AC: 3+ The most probable cause of these results is: A) rouleaux B) a warm autoantibody C) a cold autoantibody D) multiple alloantibodies

B) a warm autoantibody Presence of agglutination at AHG phase with both screening cells and autocontrol is indicative of warm autoantibody. [Harmening 2012, p222]

In ABO hemolytic transfusion reactions, complement is activated via which of the following pathways? A) alternative B) classical C) lectin D) polyclonal

B) classical ABO antibodies are very efficient at activating complement via the classical pathway. ABO antibodies can be potent hemolysins and cause intravascular destruction of incompatible red cells. [Harmening 2012, p61, 370]

Results of a serum sample tested against a panel of reagent red cells gives presumptive evidence of an alloantibody directed against a high incidence antigen. Further investigation to confirm the specificity should include which of the following? A) serum testing against red cells from random donors B) serum testing against red cells known to lack high incidence antigens C) serum testing against enzyme treated autologous red cells D) testing of an eluate prepared from the patient's red cells

B) serum testing against red cells known to lack high incidence antigens Lack of agglutination between patient serum and with cells that lack one of the high incidence antigens would confirm the specificity of the antibody. [Harmening 2012, p 225]

Refer to the following data: Hemoglobin: 7.4g/dL reticulocyte count: 22% DAT Polyspecific: 3+ IgG: 3+ C3: 0 Antibody screen-IAT SCI: 3+ SCII: 3+ Auto: 3+ Which clinical condition is consistent with the lab results shown above? A) cold hemagglutinin disease B) warm autoimmune hemolytic anemia C) penicillin-induced hemolytic anemia D) delayed hemolytic transfusion reaction

B) warm autoimmune hemolytic anemia Reaction with anti-IgG in the DAT and with both screening cells and autocontrol at the AHG phase is indicative of a warm autoantibody. [Harmening 2012, p222]

If detected in antibody screen testing, which of the following antibodies is NOT considered clinically significant in prenatal patients? A)Anti-M B) Anti-N C) Anti-Leb D) Anti-Fya

An antibody is detected in a pregnant woman and is suspected of being the cause of fetal distress. The antibody reacts at the IAT phase but does not react with DTT-treated cells. This antibody causes in vitro hemolysis. What is the most likely antibody specificity? A) Anti-Le^a B) Anti-Lu^a C) Anti-Lu^b D) Anti-Xg^a

C) Anti-Lu^b Of the antibodies listed, only Lu^b is detected in the IAT phase, causes in vitro hemolysis, may cause HDN, and does not react with DTT-treated cells.

Which group of antibodies is commonly found as cold agglutinins? A) Anti-K, anti-k, anti-Js^b B) Anti-D, anti-e, anti-C C) Anti-M, anti-N D) Anti-Fy^a, anti-Fy^b

C) Anti-M, anti-N Antibodies to the M and N antigens are IgM antibodies commonly found as cold agglutinins.

A 56-year-old female with cold agglutinin disease has a positive direct anti-globulin test (DAT). When the DAT is repeated using monospecific anti-globulin sera, which of the following is most likely to be detected? A) IgM B) IgG C) C3d D) C4a

Which of the following antigen groups is closely related to the ABO antigens on the red cell membrane? A) Rh B) Kell C) I, i D) Duffy

C) I, i The I and i antigens exist on the precursor A, B, and H oligosaccharide chains at a position closer to the red cell membrane. The I antigen is associated with branched chains, and the i antigen is associated with linear chains. The products of RH genes are nonglycosylated proteins. This means no carbohydrates are attached to the protein. Rh antigens reside on transmembrane proteins are an integral part of the RBC membrane. Kell blood group antigens are found only on red blood cells. They have not been found on platelets or on lymphocytes, granulocytes, or monocytes. The Duffy antigens (Fya and Fyb) have been identified on fetal red blood cells as early as 6 weeks gestational age. The antigens have not been found on platelets, lymphocytes, monocytes, or granulocytes, but they have been identified in other body tissues

Which of the following statements is TRUE regarding Hemolytic Disease of the Fetus/Newborn (HDFN) caused by ABO antibodies? A) Fetal hemolysis is typically severe B) It rarely occurs during the first pregnancy C) It is most common with O mothers and A babies D) A negative cord blood direct antiglobulin test excludes it E) It occurs less commonly than Rh HDFN

C) It is most common with O mothers and A babies HDFN caused by ABO incompatibility between mother and child is, in fact, the most common form of HDFN (though it is so mild that some don't even call it "HDFN"). In virtually all situations, ABO HDFN is seen with a group O mother and a group A or B child. Group O individuals carry IgG ABO antibodies that, unlike the primarily IgM antibodies in non-group O people, are transported across the placenta and enter the fetal circulation. These antibodies (either anti-A, anti-B, or anti-A,B) are "naturally occurring," like all ABO antibodies, so the interaction may occur during the first pregnancy (unlike the classic form of HDFN due to Rh antibodies, which usually occurs in second pregnancies and beyond). However, the relatively weak ABO antigen expression on the surface of fetal and neonatal red cells means that the clinical and laboratory sequelae (including hemolysis) of ABO HDFN are usually not severe. In fact, affected babies may have a negative direct antiglobulin test (DAT). (BB Guy)

Which of the following antigens are well developed on fetal cells? A) Lewis B) ABO C) Kell D) I

C) Kell Antigens develop at various rates both in utero and after birth. Kell blood group antigens can be detected on fetal cells at 10 weeks gestation and are well developed at birth. ABO antigens are present on fetal cells but expression is only 25%-50% of that we see on adult RBCs. Lewis antigens and the I antigen are all poorly developed on fetal cells.

A patient's antibody identification panel demonstrated anti-M. The antibody was most reactive with homozygous M+ cells compared to the heterozygous M+ cells. Which of the following cells would demonstrate the strongest reaction? A) M-N+S-s+ B) M+N+S+s+ C) M+N-S-s+ D) M+N+S-s-

C) M+N-S-s+ The strength of reactions for some antibodies varies due to dosage. The strongest reactions are obtained on double-dose/homozygous red cells compared to a single-dose/heterozygous red cells. [AABB Tech Manual 2017, p350]

Reagent antibody screening cells may not detect all antibodies. Which of the following antibodies is most likely to go undetected? A) anti-Co^a B) anti-S C) anti-C^w D) anti-Xg^a

C) anti-C^w Anti-Cw is an antibody to a low incidence antigen in the Rh blood group system. These antigens are present on the red cells of <1% of the population. Not all low incidence antigens are represented on the typical antibody screening cells. [AABB Tech Manual 2017, p369]

AHG (Coombs) control cells: A) can be used as a poitive control for anti-C3 reagents B) can be used only for the IAT C) are coated only with IgG antibody D) must be used to confirm all positive antiglobulin reactions

C) are coated only with IgG antibody AHG control cells are IgG-sensitiized cells that react with the anti-IgG in the AHG reagent to demonstrate AHG was added and not neutralized by insufficient washing of the tests prior to its addition. [AABB Tech Manual 2017, p486]

Anti-Fy^a is: A) usually a cold-reactive agglutinin B) more reactive when tested with enzyme treated red blood cells C) capable of causing hemolytic transfusion reactions D) often an autoagglutinin

C) capable of causing hemolytic transfusion reactions Anti-Fy^a is an IgG antibody that reacts best at the AHG phase, does NOT react with enzyme treated red cells, is capable of causing hemolytic disease of the newborn, and is not known to be an autoagglutinin

Capture-R Ready Screen (solid phase system for the detection of unexpected IgG antibodies to red cells)

Capture-R Ready-Screen is a modified solid phase antibody detection system based on procedures of Plapp et al adn Juji et al. membranes of red blood cells have been bound to and dried on the surfaces of polystyrene microwells. The membrane antigens are used to capture red cell specific antibodies patient or donor sera or plasmas. Following a brief incubation period, unbound residual immunoglobulins are rents from the wells and replaced with suspension of anti-IgG-coated indicator red blood cells. Centrifugation brings the indicator red cells in contact with antibodies bound to the reagent red blood cell membrane. In the case of a positive test the migration of the indicator red blood cells to the bottom of the wells is impeded as anti-IgG-IgG complexes are formed on the surface of the immobilized reagent layer. As a consequence of antibody bridging, the indicator cells adhere to the screening cells as a second immobilized layer. In the absence of detectable antigen-antibody interactions (negative test), the indicator red blood cells will not be impeded during their migration and will tell it to the bottom of the wells as tightly agglutinated red blood cell buttons (Immucor Package Insert Rev 07/19)

Which of the following is considered a High-Incidence antigen? A) K (big K) B) C (big C) C) c (little c) D) k (little k)

D) k (little k) A high incidence antigen is one that appears in 98% or more of the population. k (little k) occurs in approximately 98.8% of white donors and almost 100% of black donors K(big K) appears in approximately 9% of white donors and is rare in black donors C (big C) appears in approximately 68% of white donors and 27% in black donors c (little c) appears in approximately 80% of white donors and approximately 97% of black donors.

Appropriate antigen-antibody ratios are important to avoid an excesss of unbound antibody, known as: A) dosage effect B) pH effect C) postzone effect D) prozone effect

D) prozone effect Excess antibody, known as prozone, may lead to false-negative agglutination results. [Harmening 2012, p66]

Low Ionic Strength Saline (LISS) acts as an enhancement medium and facilitates antibody uptake by: A) activating complement B) increasing flexibility in hinge region C) removing water molecules D) reducing zeta potential

D) reducing zeta potential Low ionic strength saline facilitates hemagglutination by reducing the zeta potential, allowing for antibodies to react with their respective red cell antigens. LISS may also increase antibody uptake and reduce incubation times. [Harmening 2012, p 68]

Antibody Identification

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