Classes of Antibodies

IgG

• makes up majority of antibodies in serum

• only antibody that crosses placenta from mother to fetus

• function in opsonization, neutralization, and complement fixation

IgA

• found in secretions such as breast milk and saliva

• functions in agglutination and neutralization

IgM

• first antibody secreted on exposure to an antigen

• potent agglutinating and precipitating agent

• function in complement fixation

IgE

• binds to mast cells and basophils

• triggers their degranulation, facilitating inflammation, particularly in the allergic response

IgD

• antibody found exclusively on the surface of B cells

• has a role in B cell sensitization and activation