Immunohematology Part 1 ABOD Blood Groups

How do you get AB? O?

A and B are codominant so both are expressed if heterozygous. the O gene is an amorph meaning there is no O Ag, O just means you do not have A or B. Ie no product is produced from the gene, so only individuals who are homozygous for O can be O type (because if you are AO for instance, you would be A)

What blood type are you with these results? Forward typing: Positive reaction with anti-A Positive reaction with Anti-Rho Negative reaction with Anti-B Reverse Typing: Positive reaction with B Ag only

A+

What are the 4 ABO blood types? What are the different genotypes?

A, B, AB, O OO, AO, AA, BO, BB, AB (Since inheritance is by simple Mendelian genetics)

What are the most antigenic antigens in regards to blood groups? The second most?

ABO are the most, they are more antigenic than Rh(D). Rh(D) are the second most antigenic. The rest are less so we do not type by them.

In order to ensure there is no dangerous misidentification with blood typing, what must you do? What is the exception to this rule?

ABO grouping requires testing of both patients serum and RBCs. (Forward is testing pts RBCs and Reverse is testing pts serum so do both in order) Newborn babies, because they do not produce Abs until 3-6 months of age so only forward typing is done

What happens if a person with Bombay blood type receives blood from a type O- person?

Agglutination and complex forming because Bombay individuals have Abs formed against L-fucose since they do not have it.

What percentage of secretors secrete the H gene?

All of them since H gene is the necessary precursor for ABO

What is a D mosaic?

An individual who only inherits some of the component Ags of D Ag group. D Ag is itself a mosaic and is composed of several different component Ags inherited as a black. Most people get all of them (Rh+) or none of them (Rh-)

What are warm agglutinins?

Antibodies that react against RBC protein antigens at body temperature. Nearly always IgG

How much agglutination is needed for a rxn to be considered positive?

Any, even a tiny bit of agglutination is considered positive

Why do Rhnull people have hemolytic anemia?

Because Rh system antigens are integrated in the cellular membrane lack of Rh system antigens results in a hemolytic anemia due to a defect in the membrane

If you have ABO group A on the surface of your RBCs, what blood type are you? What antibodies do you have?

Blood type A. B antibodies. (This is excluding any involvement of Rh)

What is an antithetic antigen and what are examples?

C and c (and E and e) These Ags are encoded by alleles at the same locus so on one chromosome - therefore can only have a c or C but NOT both if both are present on each chromosome (so like Cc I think) they are both expressed because codominant also remember C/c/E/e are part of the Rh/D mosaic

What are the other two gene products commonly inherited with the D Ag?

C gene and its allele, c and the E gene, and its allele e Abs have been produced to these and DCE is recognized nomenclature they believe these are inherited as a block (Fisher-Race theory of inheritance) so 3 allelic genes so closely linked on a c'some that crossovers are very rare

What are the 4 characteristics of Rh null syndrome?

Chronic hemolysis Stomatocytosis (RBC membrane leaks ions) Spherocytosis (round RBCs) Increased osmotic fragility

What are cold agglutinins? What is an example of a cold agglutin and what population has these most often?

Cold agglutinins are antibodies that cross react with RBC that only cause agglutination (clumping/gooey) of RBC at low temps, below body temperatures. IgM Geriatric Patients

What do D and d refer to?

D - Rh+ d - Rh- d is believed to be an amorph or deletion because no Ab has ever been formed to it so when you test for Rh you cannot tell if an individual is homozygous or heterozygous

Explain how parital D/D Mosaic gives weak D. What is a complication of this quantitative reason for weak D?

D mosaic old term by the way A portion of D components is missing basically so Abs cannot work properly and you get a weak interaction. If the patient is transfused with D positive RBCs they can develop an anti-D alloantibody (meaning an Ab produced with specificity other than self) to the part of the epitope that is missing

Explain how positive effect can cause weak D

Due to where genes are located on the chromosome. The D gene is in trans position to the C gene so on opposite sides in this case whereas to be stronger they would need to be on the same side. The trans position causes steric hindrance which suppresses or weakens the D expression quantitative

How do we test blood group antigens ie blood typing?

Either forward typing or reverse typing

A person is blood type B+, what would your results in forward and reverse typing be?

Forward: Positive rxn with Anti-B and Anti-Rho Reverse: Positive rxn with A Ag only

What is the Fisher-Race theory of inheritance?

Genes are inherited as a block and are codominant so all expressed Each gene produces a specific antigenic determinant on the RBC

Why would someone be Weak D? What is quantitative and qualitative?

Genetics, Position Effect, or Mosaic All can cause big D to be variably expressed Quantitative is inherited weak D or position effects while qualitative is mosaic D - they could produce anti-D alloAb

What controls what blood group antigens are on the surface of RBCs? What does the specific antigen determine?

Genetics. Determines the specificity of the blood group

What is necessary for A and B expression?

H-gene expression of H-Ag (HH or Hh)

In order to express A or B genes, there is another gene that must be expressed. What is this gene and why does it determine whether or not you express A/B Ags?

H-gene that produces the H-Ag (aka H substance) and codes for the enzyme L-fucosyl transferase. This enzyme adds L-fucose to the oligosaccharide side chains on RBCs. Once L- fucose is attached, then the A or B Ags can be formed by transferring N-acetylgalactosamine to L-fucose (A-gene) or D-galactose (B gene) Whether you are homozygous (HH only) or heterozygous (Hh) so the H is dominant and it is very rare to be hh

How do blood group antigens change throughout life?

I Ag: poorly developed at birth but increases expression through maturity Lewis Ags: diminish during pregnancy A and B Ags: can be altered during certain disease states

What is the only antibody class that can cross the placenta? What is a major disease this Ab is involved in because of this?

IgG Hemolytic disease of the newborn (it is the only Ig involved in it since it can cross the placenta)

What is AHG used to detect? How is it done?

IgG attached to RBCs so sensitized RBCs It basically identifies abnormal Abs, so it is an Anti-Antibody that will complex with any human IgG Details: Wash RBCs 3x so no other free Abs or proteins to neutralize the AHG and give a false negative. Will leave only sensitized RBCs to reach with AHG. Remove all saline.

Which in vitro reactions are easier to see with the IgM/IgG and RBC antigens? Why?

IgM always has visible reactions when it reacts with RBC Ags but IgG is harder because it does not. This is because IgG is small and the distance that RBCs are normally apart in solution. The RBCs get coated in IgG and you will not know these is a problem until later (this would be sensitization on the first reaction, called when people have RBCs coated with IgG Abs). Therefore, IgM are used in testing for blood typing

What are the most important antibodies in immunohematology? When are they important?

IgM and IgG IgM: this is the "natural" Ab so nonimmune antibodies that need no previous Ag exposure like anti-A and anti-B IgG: predominant in a secondary immune response so this is an immune Ab (ex. used was sensitization by a blood group Ag and production of immune Abs to it) so you can make immune and nonimmune Abs to blood group Ags, nonimmune are just already there

Why is IgM more effective at fixing complement?

IgM is large and a pentamer so it is better at fixing complement than IgG, which requires 2 molecules of IgG close together on the surface of an RBC to fix complement

What is an example of a regular clinical use for the AHG procedure?

Infant cord blood is checked after birth to ensure the RBCs have not been sensitized with the mothers IgGs, since they can cross the placental barrier and if the baby has an Ag on its RBC surface that the mother does not have, the Abs will complex with it.

Explain how genetics can cause weak D

Inherit lower density of D ags on RBCs so basically the gene codes for less D quantitative

Are cold agglutinins clinically significant?

No, because they are not active when alive. However, they are nuisance antibodies because they can cause agglutination in blood samples. Anticoagulants in the blood sample will not help because agglutination is more of a gooing than a coagulation. You have to warm it in order to reverse the agglutination.

What is the weak expression of D? How do you test for it?

Not all D positive cells react well with anti-D so if the RBCs do not immediately agglutinate with anti-D they still have to be tested for weak D. Test: Incubate cells with Anti-D, wash 3x, add AHG which will bind to anti-D coated cells if present. If this is negative then they are D negative and if positive then positive.

Diagram of L-fucose

Notice that the 2nd one down with just L-fucose would be type O while the top would be Bombay since they have nothing

What are the universal donor and acceptor blood type groups?

O- is the universal donor because they have no ABOD Ags AB+ is the universal acceptor because they have no ABOD Abs

What is the Rh null phenotype? How are they different from Rh-?

RBCs do not carry any Rh system antigens - this can be different than Rh- because someone who is Rh- may still have some other components of the Rh complex (like c or e) so when you give an Rhnull person their blood, the Rhnull person can react to those components. Also compromises membranes of RBCs

What is the RH blood group named after?

Rhesus monkey on which antigen first discovered by Karl Landstein and Alexander Weiner (by injecting Rhesus RBCs into rabbits which produced an Ab to the monkeys and about 85% of the white population of NYC)

How do we show if there are antibodies in serum?

Serological testing, looking for agglutination when the antigen is a particulate (RBCs) is most commonly used. Add serum to set of RBCs to check for agglutination. Hemolysis, complement activation will cause RBC lysis if there are Abs against the Ags on the RBC surface, and you will see pink red color of supernatant as a result of the Hb released. But hemolyzed specimens cannot be used, like if the blood sample is already hemolyzed.

What are blood group antigens? Where do you find them?

Sugar groupings found on the membrane of RBCs.

What is cross matching?

Testing for agglutination of the donor's RBC's by the recipient's serum. This must be done before giving the blood because you have only tested for ABOD and there are other Ags.

Is D expressed better when D and C are on different or the same alleles?

The same allele, ie cis position

What determines if a person is a secretor or not? How is this useful if they are?

The secretor Se gene, can have homozygous or heterozygous. This gene is inherited completely independently of the ABO and H genes. Useful in forensics, crime, etc. Also helps with blood group typing people who have poorly developed or missing RBCs

What is RhoGAM?

The shot of Rh+ antibodies (anti-Rh) given to Rh- mothers who give birth to Rh+ children to avoid erythroblastosis fetalis/HDN in the next child. The Rhogam will bind to any fetal cells that leak into the mothers system before her immune system can be exposed to them.

What is Landsteiner's Law?

There is a reciprocal relationship between Ags and Abs. An individual naturally produces ABO antibodies to the ABO antigens which he/she lacks on their RBCs so if on RBC, not in serum and vice versa Refers to IgM class

What are Anti-Rh Abs?

They are not naturally occurring but once there can cause severe hemolytic transfusion reactions. These are responsible for HDN. They are immune Abs formed when someone is sensitized to an Rh Ag that he/she lacks like D/E/e/C/c These Abs are IgG class so they are warm agglutinins reactive in vivo that can cross the placental barrier They react best after addition of AHG

What are secretors and what percentage of the population falls under this category?

They secrete A, B, and H Ags into the body fluids that are the same as the Ags on the RBC membrane. The exact same Ags on the membrane will be in body fluids, including H (this does not involve Rh I do not think) 80% 20% are nonsecretors who are homozygous recessive

What is a regular clinical use for an IAT?

To check a mother who has already given birth to one child to see if she is sensitized. Add moms serum to Rh RBCs then AHG. If there is no agglutination, you give her Rhogam Asked Else, waiting on answer

What is forward typing?

Uses Ab to detect Ag "Fabulous" So you are identifying the blood group antigens on the RBC surface Details: Use 3-5% RBC suspension and reagent antibodies, anti-A, anti-B, anti-Rho, etc. Add 1 drop of RBC suspension and 1 drop of an Ab reagent into a tube, serofuge and tilt. If a person is blood type A, their blood will react with Anti-A You do this first *basically the result will be rxn with what you ARE

Are warm agglutins clinically significant?

Yes, because they react at body temperature so in situ they can cause an immune response. They are considered immune antibodies so they require prior exposure but can cause a hemolytic transfusion reaction.

What is the Direct Antibody Test DAT?

aka Direct Coomb's Test It is an AHG procedure so the patients sample + anti-Hu IgG (called Coomb's reagent) = agglutination is not good because sensitized so you want no reaction In hemolytic disease of the newborn HDN which used to be known as erythroblastosis fetalis, the baby's sample will show agglutination and be positive for the mothers Abs on the surface of his/her RBCs

What is an indirect antibody test IAT? How do you do it?

aka indirect coomb's test, 2 steps instead of 1 you want to see if the patients sample is sensitized so you take reagent RBCs coated with Rh and add the pts serum to them, then you add AHG. If the pt was sensitized, there will be Abs against Rh and you will get agglutination with AHG. Step 1: Rh+ RBCs + Patient serum sample = sensitized or nonsensitized RBCs Step 2: That mixture + anti-Hu IgG = agglutination if sensitized

What is the Bombay blood group?

homozygous (hh) recessive cannot produce the enzyme to express the H-Ag so products of A and B genes will not be expressed either. Very rare, they test as Group O even if A or B genes are inherited. This means they have Abs to A, B, and H. Bombay individuals are also nonsecretors since they do not produce A, B, or H

What is reverse typing?

testing patient's serum with RBCs of known A, B, and D antigens to identify the antibodies in patient's serum. Using serum Ags to identify Abs. Details: Add 2 drops of pts serum and 1 drop reagent RBC suspension. If patient type A, will react with B Ags because have anti-B antibodies. You do this to confirm to forward typing *basically the result will be rxn with what you are NOT

What is the Rh blood group?

this group includes several Rh antigens grouped together (factors). The most prevalent of these is antigen D, a transmembrane protein (others are C and E). If the Rh antigens are present on the red blood cell membranes, the blood is said to be Rh-positive. Conversely, if the red blood cells lack Rh antigens, the blood is called Rh-negative. The presence (or absence) of Rh antigens is an inherited trait from a single gene with 2 alleles.