Immunoglobulin Structure and diversity
-Has two identical arms that bind antigen-(similar to B cell Ig receptor)
-Has an Fc portion (crystalizable fragment) that can bind complement
-Structurally it is comprised of 4 polypeptide chains: 2 heavy chains and 2 light chains that
are held together by disulfide bonds
-Each light chain binds to one heavy chain. The binding of the two creates the antigen binding
site of the antibody which is unique for each specific antibody
Antigen-Antibody Interactions
-The specific interaction of antigen and antibody is specific, just like an enzyme for its substrate
-The same intermolecular interactions: van der Waals bonds and hydrogen bonds that cause
enzyme to bind substrate are the same that dictate antigen/antibody interactions.
-The higher the “specificity” of an antibody for antigen, the better the fit between the antigen
and antibody. This results in a greater “affinity” of the antibody for antigen.
Uses of antigen antibody interactions
Antigen bound to antibody is said to be “Opsonized” and more readily engulfed by immune
cells. Antibody binding to virus can “neutralize virus” by preventing it from binding susceptible
cells. Antibody can bind cells and through “complement fixation”-punch holes in the bacteria
or virally infected cells
Clonal selection theory of lymphocyte development
Explains vast repertoire of immune cells having different specificities and why
clones having a receptor for “self” antigens do not survive
What types of antibody are produced and what are their functions?
Antibody response to antigen: Primary and secondary Immune response
Primary response: IgM is produced early . As infection continues, IgG is produced
and IgM decreases.
Secondary response: Both IgM and IgG produced early and IgG remaining high for an
extended period of time