(4) Immunoglobulins & Antibody Function

Antibody components

2 heavy chains, 2 light chains, disulfide bonds holding them together

Fab region

fragment of antigen binding, the two “arms” of the Y

Fc region

fragment crystallizable, the “stem” of the Y responsible for activating complement and opsonization of pathogens

IgG structure

single y-shape

IgG primary location

blood serum

IgG function

• long-term immunity

• crosses placenta for fetus immunity

• opsonizes pathogens

• activates complement

IgM structure

5 y-shapes linked

IgM primary location

blood serum

IgM key functions

• first produced in immune response

• lacks Fc portion, does not opsonize pathogens

• activates complement

IgA structure

1-2 y-shapes

IgA primary location

body secretions

IgA key functions

• primary Ig in breast milk

• found in fluids and secretions

IgE structure

single y-shape

IgE primary location

bound to mast cells

IgD structure

single y-shape

IgD primary location

B cell surface

IgD key function

unknown

Which immunoglobulin would be most effective at binding the most antigens simultaneously and why?

IgM has a valence of 2, allowing it to bind to 10 antigens

Which immunoglobulin is responsible for long-term immunity and starts being produced in the first week?

IgG