A) There can be 10 or more different epitopes on each antigen.
B) T- cell receptors bind to epitopes.
C) B- cell receptors bind to epitopes.
D) There is a one- to- one correspondence between antigen and epitope.

A) Mast cells release one chemical messenger immediately after injury that constricts vessels to promote clotting; after bleeding has stopped, they release another messenger that causes those same vessels to dilate, which increases blood flow to promote healing.
B) Mast cells release different chemical messengers, one that causes vessels away from the site of the injury to constrict to control blood loss, and another that causes vessels near the injury to dilate to promote quicker healing.
C) Mast cells release different chemical messengers, one that causes constriction in the region of blood loss, and another that causes dilation away from the injury to promote quicker healing.
D) Different blood vessels respond to the same messenger from mast cells in different ways-for example, larger vessels constrict to reduce blood loss while smaller ones dilate to promote blood flow to the injured tissue.

A) the rearrangement of C- region genes in that clone of responsive B cells.
B) a switch in the kind of antigen- presenting cell that is involved in the immune response.
C) a patient's reaction to the first kind of antibody made by the plasma cells.
D) the recombination of variable regions of the light- chain and heavy- chain genes.
E) mutation in the genes of that B cell, induced by exposure to the antigen.