Cell Biology lecture notes: antibodies. p.1206-1216

Immunoglobulins; 20% of plasma proteins. 10⁵ high estimate of Ab embedded in B cell membranes. Ab is B cell receptors; thousands in membrane+ invariants transfer signal into cell.

Plasma cells yield 2,000 Ab molecules per second.Hemolytic plaque assay: SRBC lysis around complement-fixing Ab-producing cell. APC + T_H needed for T-dependent Ab production.

H2L2 structure. Fc, Fab, hinge, amino, C-termini, domains, disulfide linkages,papain, pepsin cleavage. 5 classes of antibodies: "Madeg". Varied heavy chains. Kappa, lambda light chains.

IgM: first produced. Embedded in B cell (IgD soon joins), also first in serum. Pentamer assembled with J chains, last of which kept. 10 "hands"; Crab-like bending. Complement fixed

IgD; Poorly understood. Not secreted by B cell. Immune regulation?

IgG; 70-80% of serum Ig. Secondary response. Transcytosis across placenta. Plentiful in colostrum. Crosses neonates gut. Also can fix complement.

IgA; "mucosal paint". Serum, secretory IgA not in equilibrium. Secretory component (piece) so IgA dimers in

IgE; "reagin". Allergies. Lowest concentration, extremely potent! Desensitization hope to deflect immune response to IgG production. IgE binds mast (recruit eosinophils; antiparasitic), basophils.

Affinity and avidity. Affinity maturation.

Complement. Classical/alternative pathways. C3 point of convergence; cleavage product accomplishes opsonization.