Antibody and Antigen Interactions Flashcards
Understand the different parts that make up an antibody
four protein chains held together by disulfide bonds; 2 identical heavy chains and 2 identical light chains (variable regions- bind to antigen); also consists of a constant region (isotype)
What is the difference between the heavy and light chains?
heavy- 4 immunoglobulin chains (determine isotype_
light- 2 immunoglobulin chains
How many heavy and light chains make up an antibody?
2 identical heavy, 2 identical light
What are the components that make up the antigen-binding site or paratope?
variable region of both the heavy and light chain
What are the main isotypes and how do they differ in structure?
Isotypes: IgA, IgD, IgE, IgG, IgM
IgA- alpha heavy chain, mono and dimeric; 4 valences; in serum in moderate amounts; cross epithelial surfaces to protect muscosal surfaces (gut, UT, resp. genital tracts)
IgD- delta heavy chain; monomeric, mostly on B cells, can serve as BCR; no interchain disulfide bond
IgE- epsilon heavy chain; monomeric; found in mucosal surfaces; involved in allergic reactions, protect against helminthic parasites; small amount in serum
IgG- gamma heavy chain; monomeric; 2 binding sites; major class found in serum, lymph and tissue spaces; can cross placenta and be found in colostrum; provides protective and neonate immunity
IgM- mu heavy chain; pentamer; 10 antigen binding sites; but only 5 valences; first antibody secreted in specific immune response; on Bcell membrane it is a monomer; primarily in serum and lymph; high avidity; most efficient at activating complement
What are the main differences in function between the N-terminal portion of the antibody and the C-terminal portion of the antibody?
N-terminal portion: variable portion of heavy and light chains, form the paratope or antigen binding site
C-terminal portion: non-variant portion of the heavy and light chain, determine the isotypes, do NOT affect binding specificity
Where is the variable region and what is its function?
variable regions of the heavy and light chains; form paratope
Where is the constant region and what is its function?
non-variable region of heavy and light chains; create isotypes, determines where antibody will be in the body
Where are the different isotopes located in the body?
IgA- secreted; mod amts in serum; protect mucosal surfaces in gut, resp., UT, genital tract
IgD- surface of B cells
IgE- mucosal surfaces bound to receptors; small amt in serum
IgG- serum, lymph, tissue spaces; secreted (cattle) in colostrum/milk; in colostrum, can cross placenta
IgM- secreted; primarily in lymph, serum
What are the different effector functions of each of the isotypes?
Complement activation- IgG and IgM (IgM more efficient)
Mast Cell degradation- IgE
Antibody dependent cell-mediated cytotoxicity- IgG, IgE, IgA
Opsinization- IgG
Signal B cell to divide and produce Ab- IgD
Toxin/virus neutralization- all
What does antibody cross-reactivity mean? How can this be good? How can it be bad?
cross-reactivity: occurs when an Ab recognizes an epitope on a different antigen that is similar or identical to the antigenic epitope for which the Ab’s paratope is specific, bind with low affinity;
Good- immunization
Bad- confusion in diagnostic testing
What are the different effector functions of antibodies?
Signal B cell to divide and produce Ab Aggregation of antigen Opsonization of antigen Toxin/virus neutralization Complement activation Blocking of attachment- in gut Mast cell degeneration- protection against parasite infection; can cause hypersensitivity reactions Antibody dependent cell-mediated cytotoxicity
What is a monoclonal antibody? How is this concept useful in a clinical setting?
come from one cell or its daughter cell, are identical; abnormal when one clone dominates the immune response; likely representative of neoplasia
What is meant by a polyclonal but monospecific response?
product of many different cells attack 1 organism or antigen
What are the characteristics that make an antigen immunogenic?
foreignness size chemical composition complexity conformational determinants genetic makeup of host age of host how the Ag is acquired
