Match each immunoglobulin isotype $(1-5)$ with the description$($s$)($a$-$l$)$ listed below that are true about it$.$ Some of the descriptions may apply to more than one isotype; others may not apply to any isotype. Enter the question number $(1-5)$ followed by the letter of the correct answer$($s$)($a$-$l$)$ into the answer box separated by a comma. $(2$ points per correct answer, $1$ point will be subtracted for each incorrect answer, $30$ points total$)$

Example answer format:

IgA $$

IgD

IgE

IgG

IgM

$$

a$.$ Secreted form is a pentamer of the basic H$2$L$2$ unit

b$.$ The most abundant Ig class in the serum

c$.$ Dimers present in secretions are resistant to degradation

d$.$ Production is hallmark of allergic reactions, induced by IL$-4$

e$.$ Most effective in activation of complement by the classical pathway

f$.$ Is never expressed on the surface of B cells

g$.$ Present on the surface of mature, na$$ve B cells

h$.$ The first serum antibody made in a primary response

i$.$ Derived from isotype switching during formation of memory cells

j$.$ Although poorly understood, may function in early B cell development

k$.$ Predominant isotype in breast$-$milk, confers passive immunity to nursing infants

l$.$ Stimulates mast cells and basophils to release inflammatory compounds