Exam 3 Ch 17: Adaptive Immunity
By what 5 mechanisms can Ab-Ag binding render the foreign organisms/toxin harmless?
1. Agglutination (easier for IgM a pentamer and IgA a dimer) 2. Opsonization 3. *Antibody-dependent Cell-mediated cytotoxicity: abs attach to target cell cause destruction by attracting eosinophils and NK cells* 4. Neutralization *(IgG)* 5. Activation of Complement* (IgM, IgG)*
_____ antibodies are the most prevalent in serum; -they provide naturally acquired passive immunity that protects fetus/newborn - neutralize bacterial toxins and viruses -participate in complement fixation -enhance phagocytosis
*IgG 80%* IgA 10-15% IgM 5-10% IgD 0.2% IgE 0.002%
Name the macromolecule: As a rule, antigens are _________ or large _____________ and can have ______ or _____ combined into them. Antigens can also be other stuff, such as ________ Antibodies are ____________ produced by ________ in response to ___________.
*proteins or large polysaccharides* and they can have lipids/nucleic acids combined into them. Antigens can also be capsules, virus protein coat, cell walls, flagella, fimbriae, toxins of bacteria, pollen, egg white...doesn't have to be microbial) antibodies are proteins produced by Plasma cells (which come from B cells that have been activated) in response to antigen
Professor Walcott says that inflammation is a complement related protective mechanism that can occur when Ab-Ag binding occurs. Describe what happens and which complement is involved.
If your bacteria is coated with IgM/IgD it can activate complement protein via the classical pathway. C5A and C3A cause mast cells or basophils to release histamine which causes inflammation which increases vessel permeability so phagocytes can come in to area. the C5A also attracts phagocytes.
Which Ig is found in secretions (milk/tears/mucus/intestines)?
IgA
Which Ig is most abundant in your body, although not most abundant in your serum?
IgA
Which Ig is produced by plasma cells in mucus membranes, mostly by epithelial cells?
IgA
Which type of immunoglobulin would you find in peyer's patches and are essential for mucosal immunity?
IgA
____ antibodies are on B cells; they may delete B cells that produce antibodies against self
IgD (serum function is not known)
Which Ig is located on mast/basophils which are specialized for allergic reactions?
IgE
Which Ig is useful against parasitic worms?
IgE
____ antibodies bind to mast cells and basophils and are involved in allergic reactions
IgE
Which Ig can cross the placenta?
IgG
Which Ig can neutralize bacterial toxins?
IgG
Please tell me the shape of each of the immunoglobulin classes
IgG monomer IgM pentamer IgA dimer with secretory component IgD monomer IgE monomer
___ antibodies can attach to microbes or toxins and prevent them from attaching to stuff causing ______
IgG neutralization (IgG antibodies inactivate microbes/toxins like this)
Which Igs fix complement?
IgG, IgM
If a patient has been exposed to an antigen for the first time, which class of immunoglobulin appears first?
IgM
The predominant antibody involved in response to ABO antigens on RBCs?
IgM
Which Ig appears first in response to primary infection, is short-lived and is valuable in diagnosis of disease?
IgM
Which Ig is very effective at causing clumping of cells/viruses?
IgM (pentamer)
The majority of the B cell's surface immunoglobulins are either Ig__ or Ig___. However, in the intestinal mucosa, B cells are rich in Ig___
IgM or IgD (and if they are together on a B cell they will be specific for recognition of the same epitope) In intestinal mucosa, B cells are rich in IgA.
Which Ig is found on B cell surface?
IgM, IgD, altho B cells in intestinal mucosa are rich in IgA
The function of M cells is to:
txp antigens encountered in the digestive tract to contact lymphocytes and antigen-presenting cells of the immune system. M cells are located within Peyer's patched
Prof Walcott says.... __________ is antibody protein
Immunoglobulin (Ig)
_________ facilitate contact between antigens passing through the intestinal tract and cells of the body's immune system.
M cells (microfold cells). located within peyer's patches in intestinal wall. they txp antigens in the digestive tract to contact lymphocytes and APCS of the immune system.
Activated T Helper Cells can proliferate into what?
Memory cells, TH1 TH2 TH17 TH1 = activate cytotoxic T cells and cells related to cell mediated immunity-activate macrophages TH2 = activates B cells and gets cells to produce antibodies, eosinophils (activates humoral immunity)
Does the antibody molecule damage the antigen it attaches to?
NO! the binding of an antibody to an antigen doesn't damage it. It simply protects the host by tagging the foreign cells/molecules for destruction.
In _______________ IgG antibodies inactivate microbes by blocking their attachment to host cells. They act on toxins in a similar manner as well.
Neutralization! protective mechanism that occurs when Ab-Ag binding occurs
Why would a body cell that is not a phagocyte need to present antigens? Antigens are infectious and can spread to normal cells. All cells of the body can engulf invading cells. Antigens are required for cell-to-cell attachment. Non-phagocytic body cells can become infected with a virus.
Non-phagocytic body cells can become infected with a virus.
Thymic selection weeds out _____ cells that will not specifically recognize ____________
weeds out T cells that will not specifically recognize self-molecules of MHC. This is important in preventing the body from attaching its own tissues.
When pathogens enter body via the GI or respiratory tracts, they have to pass through what? Why would we want these pathogens to enter here?
Pathogens will first encounter a barrier of epithelial cells. if they pass through this, its via gateway cells called *M cells (microfold cells)* which are located over *Peyer's patches*, which are secondary lymphoid organs located on the intestinal wall. When M cells take up antigens from intestinal tract, they transfer to lymphocytes/apcs of the immune system which are found right there under the epithelial cell layer and esp in peyer's patches.
Produce and secrete antibodies
Plasma cells
What are perforin and granzymes, and who releases these?
Released by Cytotoxic T Cells Perforin is a pore-forming protein which contributes to death of the cell from lysis (similar to action of complement membrane attack complex) Granzymes are proteases that induce apoptosis, which is programmed cell death, basically makes the cell kill itself by cutting its genome into fragments and then getting phagocytes to come digest remains.
Describe the structure of an antibody: What is the V region and C region? Locate the antigen binding sites, the V region and the C region
Structure: Y shaped molecule composed of 2 light chains & 2 heavy chains linked by disulfide bridges. The amino acid sequences of the variable regions which form the antigen binding sites, differ from molecule to molecule. Most of the molecule is made up of constant regions. V= variable region that binds to epitopes. The V structure reflects the nature of the antigen for which the antibody is specific. C= constant region...same for an entire particular class of Igs.
Who can combat intracellular pathogens?
T cells
T cells mature in the _________. What happens to T cells that can't recognize self-molecules of MHC? Why would this be a problem?
T cells mature in the thymus They get eliminated via thymic selection, which eliminates many immature T cells that wouldn't be able to recognize self-molecules of MHC which would mean the T cells would attach our own body tissues because it wouldn't recognize that its our own good cell
______ are activated by endogenous antigens and MHC Class I on a target cell
T cytotoxic cells (Tc) or CD8+ T cells
T helper cells (CD4+T) are activated by/transformed into: T cytotoxic cells (CD8+T) are activated by/transformed into:
T helper cells (CD4+T) are activated by their TCR binding to processed antigen presented on MHC Class II on APCs. After binding, APC secretes cytokines that activate T cells into TH1/2/ memory cells T cytotoxic cells (CD8+T) are activated by: "endogenous antigens and MHC class I on a target cell, and are transformed into a CTL (TH1 cytokines costimulate btw)
T-Cell receptors on T cells recognize ___________ On an unactivated TH cell, TCRs recognize__________ On TH2 what happens? What about CD8+T/Tc cells?
TCRs recognize antigens (that have been processed by antigen presenting cells) THelper cells recognize the antigen that's been processed/presented with MHC II on an APC, it binds with it and the APC releases costimulating cytokine. These 2 things activate the TH cell which becomes TH1/TH2/Memory cell. TH2 CD4+ T cell has TCR that recognizes an antigen presented by the B cell with MHC class II, so the TCR binds with that then the TH2 releases cytokines to stimulate activation of the B cell. CD8+T cells have TCRs that bind to MHC class I which is how virus infected cell or tumor cell displays endogenous antigen. (TH1 cytokines co stimulates the Tc cell to activate it into a CTL)
TH cells TCRs react with antigens presented by MHC____ TC cells react with antigens presented by MHC ____
TH-MHC II TC- MHC I
Which cell is this: prodyce cytokines (esp IFN-y) -activate cytotoxic T cells related to cell mediated immunity -activate cells that are responsible for delayed type hypersensitivy (walcott says) -activate macrophages -stimulate antibodies that promote phagocytosis -enhance activity of complement (such as opsonization/inflammation)
TH1
Which type of T cell is involved in activating macrophages and and cells related to cell-mediated immunity?
TH1 cells
_________ cells activate cells involved in cellular immunity
TH1 cells activate CTLs
The cytokines produced by ____ cells activate mostly those cells related to important elements of cellular immunity. They can also activate cytotoxic T Cells. The cytokines produced by ____ cells are associated primarily with the production of antibodies/activation of B cells/ producing eosinophils.
TH1 cytokines , esp IFN-y are important for cell-mediated immunity TH2 activate humoral immunity!
TH1 cells produce cytokines that activate ______ TH2 cells produce cytokines that activate _______
TH1 cytokines activate Tc cells TH2 cytokines activate B cells
Name the cell with this function: activates cells (cytotoxic T cells) related to cell-mediated immunity
TH1 releases cytokines that do this
When T Helper cells get activated and proliferate, whats the difference between TH1 and TH2?
TH1:: produce cytokines (esp IFN-y) -activate cytotoxic T cells related to cell mediated immunity -activate macrophages -stimulate antibodies that promote phagocytosis -enhance activity of complement (such as opsonization/inflammation) TH2: produce cytokines associated primarily with B cell's production of antibodies (IgM and esp IgE which are important in allergic rxns) -important in activation of eosinophils which defend against parasites and helminths.
Which cell is this? produce cytokines associated primarily with production of antibodies (IgM and esp IgE which are important in allergic rxns) -important in activation of eosinophils which defend against parasites and helminths.
TH2
_____ cells are associated with allergic reactions and parasitic infections
TH2 (produce eosinophils)
Name the cell with this function: stimulates production of eosinophils, IgM and IgE
TH2 cytokines do this
Why are T helper cells considered an important part of humoral immunity?
TH2 has TCRs that recognize/s attach to MHC II/antigen fragment on B cells and then release cytokines to stimulate B cell to activate into plasma cells which secrete specific antibodies.
T cycotoxic cells, or CD8+ T cells are activated by __________ and then turn into ________ Thelper cells or CD4+T cells are activated by _______n go on to do what?
Tc/CD8+T cells are activated by *endogenous antigens on the surface of a target cell that are in combination with MHC Class I...once activated they turn into cytotoxic T lymphocytes (CTLs)* that recognize Ag+MHC I and induce apoptosis in the target cell. To activate Th cells, at lease two signals are required. 1. binding of the TCR to the APC which is presenting the processed antigen in combination with MHC Class II, 2. the APC releases costimulating cytokines. Once activated Th cell secretes cytokines and proliferates into Th1, Th2, Th17, memory cells.
Lymphocytes that activate B cells and CTLs
Th cells
Once Th cells are activated and proliferate, we get Th1 and Th2, what do these do?
Th1 -activate cytotoxic T cells. -produce cytokines (esp IFN-gamma) that stimulate macrophages, and activate other cells related to cell-mediated immunity Th2 produce cytokines that help B cells production of antibodies (IgM and IgE), stimulate activity of eosinphoils which control extracellular parasites such as helminths.
What are Tc cells?
Thats another way to write T cytotoxic cells or CD8+ cells which are precursor to cytotoxic T lymphocytes (CTLs)
In order for T cells to recognize antigens, what has to happen? Which class of MHC will the CD4+T (T Helper cells) and CD8+ (T Cytotoxic cells) bind to?
The antigen has to be processed by antigen-presenting cells (APC can include activated macrophages and dendritic cells) . Antigen is attached to MHC making an antigen-MHC complex. (TH2) CD4+ cells bind to MHC II molecules on B cells (then secrete cytokines that activate the B cell) CD8+ cells bind to MHC Class I on APCs, Recall that In humoral immunity, B cell serves as the APC
Consider a helminthic infection in which an individual is colonized by a parasitic worm. The worm is too big to be engulfed by a phagocytic cell. How does the immune system respond?
The worm gets coated with antibodies, which activate other cells in the immune system to secrete chemicals that kill it.
What is agglutination?
This is a mechanism by which Ag-Ab binding can help get rid of the foreigner. antibodies cause antigens to clump together which means there are fewer units to be dealt with by phagocytes
What is opsonization in humoral immunity?
This is a protective mechanism that occurs when Ab-Ag binding occurs antigen is coated with antibodies, which enhances its ingestion and lysis by phagocytic cells
Tom has a genetic disorder in which he does not synthesize class I MHC proteins or functional NK cells. Which of the following statements would be true for Tom?
Tom would not be able to destroy virally-infected cells.
Within each antibody is a ____ region that binds to the epitope and a _____ region that distinguishes the different classes of antibodies. And a ____ region that can attach to a host cell or to complement
Variable (V) region Constant (C) region Fc
During ____________________ the target organism becomes coated with antibodies and destruction of the target cell is by immune system cells that remain external to the target cell.
What is Antibody-dependent cell-mediated cytotoxicity? protective mechanism that occurs when Ab-Ag binding occurs
If you have IgG it indicates immunity to....
a pathogen you acquired in the past
Either IgG or IgM antibodies may trigger ___________________. which can lead to inflammation or cytolysis
activation of complement system requires C5b-C9 for lysis occur C5a and C3a required for inflammation protective mechanism that occurs when Ab-Ag binding occurs
______________ is the ability of the body to specifically react to a microbial infection
adaptive immunity
___________ is the resistance to infection obtained during the life of the individual; results from production of antibodies and T cells
adaptive immunity (3rd line of defense, includes humoral and cell-mediated immunity)
_____________ refers to induced resistance to a specific pathogen; evolves over time
adaptive immunity (your 3rd line of defense)
________ results when an antibody combines with epitopes on 2 different cells
agglutination
in ___________ antibodies cause antigens to clump together so they are more easily ingested by phatocytes.
agglutination
When an antibody encounters an antigen for which it is specific ____________ forms
an antigen-antibody complex rapidly forms.
The humoral response is carried out by ___________.
antibodies found in your humors.
_____________ is a protein produced by B cells (plasma cells) in response to an antigen and is capable of combining specifically with that antigen
antibody (or immunoglobulin)
Prof Walcott says.... ________ is a substance that causes the body to produce specific antibodies or sensitized T cells
antigen (Ag)
___________ is a chemical substance that causes the body to produce specific antibodies
antigen (or immunogen)
________ immunity is __________ mediated and depends on T cells to control intracellular pathogens
cellular imunity is cell-mediated
What type of molecule activates cytotoxic T lymphocytes?
cytokines released from T helper cells (TH1)
Kill infected host cells
cytotoxic T cells
Phagocytes that engulf anything foreign. Eventually display epitope to helper T cells using MHC I or II
dendritic cells
Specific regions on antigens that antibodies form against/recognize
epitope or antigenic determinant.
________ immunity is ___________ mediated and is directed at freely circulating pathogens and depends on B cells
humoral immunity (antibody mediated immunity)
Use BCRs to recognize epitope. First step in clonal selection
immature B cells
Complement activation results in__________
inflammation and cell lysis (Recall that IgG or IgM antibodies bind to C1 which starts the classical pathway for activation of the complement system)
__________ refers to the resistance of speices or individuals to certain diseases that is not dependent on antigen-specific imunity
innate immunity
An individual's genetically predetermined resistance to certain diseases is called ______________ An individuals ability to specifically react to a microbial infection is called _________
innate immunity= predetermined resistance. not specific adaptive immunity, specific, not born with it
Red bone marrow stem cells produce _________ which can become ______ cells or _____ cells. Where do each of the cells mature?
lymphocytes...some mature in the bone marrow and become B cells(with IgM and IgD on their surface), others mature in thymus and become T cells.
Differentiated B cells that are stored in lymph nodes to provide protection against future infections by the same pathogen
memory cells
Pathogens pass the barrier of epithelial cells in the wall of the GI tract by way of a scattered array of gateway cells called _________
microfold cells (M cells), located over Peyer's patches, which are secondary lymphoid organs located in the intestinal wall. M cells take up antigens from intestinal tract and allow their transfer to the lymphocytes and APCs of the immune system found throughout the intestinal tract, under the epithelial cell layer, and esp in peyers patches.
Mature T cells migrate from the thymus by way of ________ and __________ to the __________
migrate from thymus by way of blood and lymphatic system to various lymphoid tissues where they are most likely to encounter antigens. *note that most pathogens of the type that the cellular immune system is designed to combat first enter the GI tract or lungs.*
The flu virus mutates fairly frequently. Its adhesive proteins change such that we have different "strains" of influenza each year. When a particular flu virus mutates such that its adhesive proteins change, which function of antibodies is disrupted? complement activation neutralization opsonization agglutination
neutralization
What is it called when an antigen is coated with antibodies, which enhances its ingestion and lysis by phagocytic cells
opsonization This is a protective mechanism by which Ag-Ab binding can help get rid of the foreigner
What are plasma cells?
part of humoral immunity secrete antibodies into circulation. When B cells proliferate they become either plasma cells or memory cells
opsonizaton enhances ___________
phagocytosis of the antigen which gets coated in antibodies
What is neutralization?
protective mechanism that occurs when Ab-Ag binding occurs IgG antibodies inactivate microbes by blocking their attachment to host cells. They act on toxins in a similar manner as well.
Cytotoxic T Lymphocytes do what?
recognize Ag/MHC Class I which is found on nucleated cells meaning when a virus or something alters one of our own cells, CTLs can recognize and bind and then work their magic -CTLs release perforin and granzymes
Prof Walcott says....the 3rd line of defense consists of:
1. Humoral immunity: Involves antibodies produced by B cells (plasma cells) and found in your humors 2. Cell-mediated immunity: involves T cells
_____ antibodies protect mucosal surfaces from invasion by pathogens
secretory IgA antibodies (as opposed to serum IgA antibodies) provide localized protection on mucosal surfaces.
IgA shape: ___% of total serum antibody Can it fix complement? Location: Known functions:
shape: Dimer (with secretory component) 10-15% of total serum antibody (if mucous membranes and body secretions are included, % is much higher) NO it CAN'T fix complement *Location: Blood, Lymph, Secretions (tears, saliva, mucus, intestine, breast milk)* *Known functions: Localized protection on mucosal surfaces (prevents microbial pathogens from attaching to mucosal surfaces. this helps w resistance to intestinal/respiratory pathogens).*
The adaptive immune system is divided into two parts, each responsible for dealing with pathogens in different ways. These two systems function interdependently to keep the body free of pathogens. What are the two parts?
1. humoral immunity: antibody mediated immunity; directed at freely circulating pathogens and depends on B cells 2. cellular immunity: cell-mediated immunity; depends on T cells to eliminate intracellular pathogens, reject foreign tissue and destroy tumor cells.
IgE shape: ___% of total serum antibody Can it fix complement? Location: Known functions:
shape: monomer 0.002% of total serum antibody Can it fix complement? NOPE *Location: Blood and Bound to mast cells, basophils* Known functions: involved in allergic reactions and lysis of parasitic worms
IgD shape: ___% of total serum antibody Can it fix complement? Location: Known functions:
shape: monomer 0.2 % of total serum antibody Can it fix complement? NOPE *Location: B cell surface, Blood, lymph* *Known functions: Serum function is unknown; On B cells it functions in initiation of immune response*
IgG shape: ___% of total serum antibody Can it fix complement? Location: Known functions:
shape: monomer 80% of total serum antibody YES it Can it fix complement? *Location: Blood, Lymph, INTESTINE* *Known functions: enhances phagocytosis; neutralizes toxins and viruses; protects fetus and newborn (passed from mom to baby via placental txfer)* in regions of inflammation it readily crosses walls of blood vessels to enter tissue fluids
IgM shape: ___% of total serum antibody Can it fix complement? Location: Known functions:
shape:pantamer 5-10% of total serum antibody YES it Can it fix complement? *Location: Blood, lymph, B cell surface (as monomer)* *Known functions: -agglutinates antigens/microbes (it is predominant antibody involved in response to ABO blood group antigens on surface of RBCs), more effective than IgG in causing clumping -first Ab produced in response to infections (and it is relatively short lived, so if you see IgM you know the infection is prob new and active)*
Prof Walcott says.... ________ are proteins made in response to a foreign antigen
Abs (antibodies)
Antibodies are produced by __________ List the 5 different types of antibodies and their % in Serum.
Abs are produced by Plasma cells which are a type of activated/clones B cell (a type of lymphocyte). IgG 80%.. IgA.. 10-15%.. IgM 5-10%.. IgD 0.2%.. IgE.. 0.002%
An activated B cell can do what?
Activated B cell can proliferate into a large clone of cells. some become plasma cells (produce antibodies) some clones becomes memory cells.
What is Antibody-dependent cell-mediated cytotoxicity? How is it different from opsonization?
target cell becomes coated with antibodies.... destruction of the target cell is by immune system cells (macrophages, eosinophils, NK cells) that remain external to the target cell, no phagocytosis; perforin and lyctic enzymes. -target is usually something large like a parasite. opsonization enhances phagocytosis.
Prof Walcott says....________ is the generic term for serum because it contains Ab
Antiserum
Describe the activation of a B cell.
B cell (covered in IgM and IgD antibodies) recognizes an extracellular antigen for which it is specific. Antigen gets processed and fragments are combined with the MHC II and presented on the B cell surface. Next a TH2 (T Helper 2 cell) arrives and attaches to the MHC II and releases cytokines, which activate the B cell. (note that some B cells don't require T cell help). Once B cell is activated, it undergoes clonal expansion into Plasma Cells and Memory cells.
B cells are coated with ________ that provide specificity. T cells have _______
B cells are coated with immunoglobulins (most b cells carry IgM, IgD, B cells in intestinal mucosa are rich in IgA) T cells have TCRs (T-cell receptors) (not to be confused with phagocytes that have TLRs that attach to pamps)
Which antibodies would you find on B cells? Which antibodies activate complement?
B cells have IgM, IgD Activate complement: IgM, IgG
B cells are coated with _________ which provide specificity for the cell and recognize _______ T cells have _________ on their surface which recognize _________ Phagocytes have _______ which binds with PAMP
B cells have a coating of Igs (usually IgM or IgD) that provide specificity and recognize specific free/ extracellular antigens. T cells have TCRs (T Cell Receptors) which recognize antigens (once they have first been processed by specialized antigen-presenting cells (APCs), which process and display an antigenic fragment on their surface. Phagocytes have Toll Like Receptors (TLRs) that bind with PAMPs on pathogens.
__________________ stimulated with ___________ differentiate into __________, which secrete antibodies into the bloodstream. Phagocytes, antigen, B-cells Plasma cells, antigen, B-cells B-cells, antigen, plasma cells Antigen, plasma cells, B-cells
B-cells, antigen, plasma cells
For lysis to occur during activation of complement (for Ag-Ab binding), which complement proteins are required?
C5B, C6, C7, C8, C9
Immunological response that kills infected host cells
Cellular immunity
Which of the following would you likely see on the surface of a human dendritic cell following phagocytosis of a bacterium? Class II MHC with dendritic cell antigens Class I MHC with dendritic cell antigens and Class II MHC with engulfed bacteria Class I MHC with dendritic cell antigens Class II MHC with engulfed bacterial antigens
Class I MHC with dendritic cell antigens and Class II MHC with engulfed bacteria
What would a virally infected skin epithelial cell have on its cell surface? Class II MHC with liver cell antigens Class II MHC with macrophage antigens Class I MHC with skin cell antigens Class II MHC with viral antigens
Class I MHC with skin cell antigens
Who recognizes Antigens/MHC Class I? Where is MHC Class I found?
Cytotoxic T Cell receptors MHC Class I is found on nucleated cells, so CTLs can attach altered host cells
I destroy target cells on contact, I am generated from T cyotoxic cells
Cytotoxic T Lymphocyte (CTLs)
I can lyse or induce apoptosis in the target cell. Who am I??
Cytotoxic T Lymphocytes (CTLs)
HIV directly infects T-cells. Why is this problematic for cell-mediated immunity?
Cytotoxic T-cells begin to attack the virally infected T-cells, reducing the number of T-cells in the body.
Which of the following are likely to be found on an MHC-I protein? -Membranes from a neighboring dead host cell -Bacterial DNA - Bacterial cell wall fragment -Bacterial flagella -Damaged mitochondrial fragment
Damaged mitochondrial fragment
T cells are classified according to....
their functions and cell-surface glycoproteins called CDs (clusters of differentiation). These are membrane molecules that are important for adhesion to receptors. CD4+ cells are classified as T Helper cells (which activate into TH2 which secrete cytokines to help activate B cells, and TH1 which secrete cytokines that activate Tcs, macrophages and other cells related to imp elements of cellular immunity) CD8+ cells are classified as T Cytotoxic cells (the precursor to Cytotoxic T Cells)
Th cells are classified as CD4+ because:
they have glycoproteins on their surface called clusters of differentiation or CD. These are membrane molecules that are esp important for adhesion to receptors. CD4 is found on Th cells.
How does a CD4+ (T Helper) cell get activated? How does a CD8+ (T Cytotoxic) cell get activated
Helper ACTIVATION REQUIRES 2 SIGNALS! *binding/costimulation* CD4+ cell's TCRs recognizes/binds to processed antigen fragment held in a complex with MHC II on APC s. THEN you have costimulating cytokines from the APC. Now CD4+ cell can proliferate at rate of 2-3 cells per day into memory cells, TH1, TH2 and TH17 CD8+ (Tc) is activated by an antigen processed by an APC (dendritic cell) that presents antigen with MHC I. ALso, TH1 sends co stimulating signals Result is CTL!
The TCRs on CD4+ cells recognize.... CTL?
Helper T Cells (esp TH2) recognize antigens presented on MHC II on APCs (note that B cells are APCs that present extracellular antigens and present it on their MHC II) TCRs on CTLs recognize endogenous antigens on MHC I
According to Prof Walcott, _________ cells are targeted by HIV virus
Helper T cells
HIV can target _________ cells
Helper T cells (CD4+)
Why do mature T cells migrate from thethymus by way of the blood and lymphatic system to various lymphoid tissues?
Here they are most likely to encounter antigens. (T cells combat intracellular pathogens)
____________are effective against pathogens such as viruses and bacteria that are circulating freely, where the antibodies can contact them. Intracellular antigens, such as a virus within an infected cell, are not exposed to circulating antibodies. Some bacteria and parasites can also invade and live within cells. The body can combat intracellular pathogens with ____________
Humoral antibodies are effective against pathogens that are circulating freely. T cells and cellular immunity are used against intracellular pathogens.
Humoral immunity involves _____ cells which produce __________ after encountering free/extracellular antigens. Cellular immunity involves ___ cells which combat intracellular pathogens and nonself cells such as cancer cells or tumor cells
Humoral immunity involves B cells and antibodies (found in serum and lymph and are produced by B cells that encounter free/extracellular antigens) Cellular immunity involves T Cells (lympohocytes that migrated to the thymus to mature into T cells)
Why is humoral immunity referred to as such?
Humoral immunity is antibody mediated, and antibodies (which are produced by B cells (plasma cells)) are found in the "humors" i.e. blood, phlegm, bile etc.