Antibodies, Antibody Diversity, and T Cell Development Flashcards
What is an antigen?
Anything that can be SPECIFICALLY bound by cells of the adaptive immune system (B Cell receptor, T Cell receptor)
Which cells bind in a specific manner to antigen?
Lymphocytes
- B Cells
- T Cells
Recognition of antigen by B cell receptors will result in ______ secretion by ______ and development of immunological _______.
Antibody
Plasma Cells
memory
Recognition of antigen by T cell receptors will result in T cell activation which will secrete _____ or become ____ cells.
cytokines
Natural Killer
What are the two forms of antibody?
- Membrane bound (b cell receptor)
2. Secreted
What are four functions of antibodies?
- Antigen Recognition
- Direct antigen neutralization
- Opsonization
- Activation of the complement cascade (results in lysis)
____cells do NOT require antigen presentation, ___ cells do (MHC).
B
T (MHC)
Where do B cells complete their maturation?
Bone marrow
Where do T cells complete their maturation?
Thymus
What is hematopoiesis?
Production of RBCs, Platelets, and WBCs from bone marrow:
Stem Cell –> common myeloid progenitor, common lymphoid progenitor
CMP–>basophil, neutrophil, eosinophil, monocyte
CLP–> B lymphocytes, T Lymphocytes
True or False: These stages of maturation [Stem Cell->ProLymphocyte-> PreLymphocyte-> Immature Lymphocyte] will occur without antigen presence.
True
The lymphocyte will go from immature to mature when ______ is present in the bone marrow.
Self-antigen
The lymphocyte will change from “mature” into a “differentiated effector” when _____ is present. This occurs in _____ _______ organs or tissue.
Foreign Antigen
peripheral lymphoid
Lymphocytes with high avidity for self-antigen will result in ______ selection.
Negative (removal)
Low avidity interactions with self-antigen will result in _____ selection of lymphocytes.
Positive (clonal expansion/differentiation)
What are the primary functions of Antibodies?
- Ag binding and recognition
2. Trigger the elimination of foreign Ag
True or False: Binding alone may be sufficient for Ab to neutralize Ag.
True
If antibody triggers the elimination of Ag, what are the three possible mechanisms?
- Cell Lysis (through activation of complement)
- Phagocytosis (after opsonization)
- NK mediated cytotoxicity
What are the two fragments of an antibody?
Fab (highly variable, antigen-binding fragment)
Fc (crystallized fragment)
Describe the four chain structure of an antibody.
2 identical heavy chains (spanning Fab and Fc)
2 Identical light chains (spanning Fab only)
Differences in antibodies exist within the _____ chains.
Heavy
How are heavy chains indicated when listing different immunoglobulins?
The letter following “Ig”
IgM, IgA, IgD, IgE, IgG
Which immunoglobulin is found in mucosal areas? How many types are there?
IgA
Two types: bound and secreted
Which immunoglobulin has four types?
IgG
Which immunoglobulin is involved in allergic responses (histamine release) and parasitic infections?
IgE
Which immunoglobulin is found circulating in the highest levels and is capable of crossing the placenta?
IgG
Which immunoglobulin indicates an early stage of infection?
IgM
Which immunoglobulin activates basophils and mast cells?
IgD
Early stages of infection will involve the presence of ____ and ____.
IgD
IgM**first
Presence of ____ indicates late stages of infection.
IgG
Fab arms are linked to Fc by an extended region of polypeptide chain known as the _____.
Hinge
What are the two forms of light chains?
Kappa
Lambda
How many subclasses of heavy chains are there?
four
y1, y2, y3, y4
Antigens bind to the _______ regions of an antibody.
Hypervariable (CDR)
[complementary determing region]
By what mechanism does the body make so many different antibodies?
VDJ Rearrangement
The human heavy chain variable region is constructed of ____ gene segments; the light chain variable region is constructed by the joining of ____ gene segments.
Three (VDJ)
Two (VJ)
What are the three gene segments associated with heavy chain variability?
V (variable)
D (diversity) <–not present in light chain
J (joining)
What is “the creation of antibody diversity through the joining of various gene segments”?
V(D)J Recombination
What is somatic mutation?
After antigen stimulation, the VDJ genes in B cells can make single base changes that increase the affinity of antibody (affinity maturation)
Where does somatic hypermutation usually occur?
the hypervariable region (CDR)
BCR on a naive B cell can only be ____ or ____.
IgM
IgD
A plasma cell CAN secrete all of the antibody isotypes but a PARTICULAR plasma cell will secrete ______.
ONE form of antibody
_____ ______ allows for the generation of multiple antibody isotypes with the same Ag specificity.
Class Switching
Once a plasma cell is determined to be a particular antibody type, the other genes are removed via a ________ process.
Loop and Cut
T cells mound an immune response against ______ antigens.
Non-self
When T cells leave the bone marrow, the do not have a ____ and will acquire one in the thymus.
TCR
Those T lymphocytes that do not bind MHC through their TCR are destined for _______ .
Apoptosis
Low avidity interaction with self-antigen results in positive selection within the ______ region of the thymus.
Cortical
High avidity interaction with self-antigen results in negative selection within the _____ region of the thymus.
Medullary
In order for T cells to expand and differentiate, what are the two requirements?
- Bind self-antigen at LOW-avidity
2. Bind MHC
A T cell is destined for apoptotic cell death if it has a “lack of positive selection” because _______ or if it has “negative selection” because ________.
lack +selection = cannot recognize MHC
- selection = binds self at high avidity
A T cell is rescued from apoptotic cell death if _______.
The thymocyte recognizes MHC and engages in a low avidity interaction (positive selection)
