Maintenance of the Body
Check Your Understanding
What event (or observation) signals that a B or T cell has
Which of the following T cells would survive education in
the thymus? (a) one that recognizes neither MHC nor self-
antigen, (b) one that recognizes both MHC and self-antigen,
(c) one that recognizes MHC but not self-antigen, (d) one
that recognizes self-antigen but not MHC.
Name three different APCs. Which is most important for T
In clonal selection, “who” does the selecting? What is being
For answers, see Appendix H.
In summary, the two-ﬁsted adaptive immune system uses
lymphocytes, APCs, and speciﬁc molecules to identify and de-
stroy all substances—both living and nonliving—that are in
the body but not recognized as self. Te system’s response to
such threats depends on the ability of its cells to (1) recognize
antigens by binding to them and (2) communicate with one
another so that the whole system mounts a response speciﬁc
to those antigens. As you will see, interactions between various
lymphocytes, and between lymphocytes and APCs, underlie
virtually all phases of the adaptive immune response.
outlines major similarities and diﬀerences be-
tween B and ± lymphocytes. Tis will help orient you as you
delve into the details of humoral and cellular immunity.
Humoral Immune Response
Deﬁne humoral immunity.
Describe the process of clonal selection of a B cell.
Recount the roles of plasma cells and memory cells in
to a receptor on a
specific B lymphocyte
(B lymphocytes with
form a clone
Activated B cells
(effector B cells)
Memory B cell—
primed to respond
to same antigen
Clone of cells
by same antigen results
in more rapid response
(can be years later)
Clonal selection of a B cell.