Page 562 - Veterinary Immunology, 10th Edition

eliminated once they have served their functions. For example,
VetBooks.ir when activated T cells have completed their task of killing their

targets, they themselves undergo CD95-mediated apoptosis.

FIG. 18.10 The CD95 pathway of T cell–mediated cytotoxicity.

In mice, lpr (lymphoproliferation) and gld (generalized
lymphoproliferative disease) are loss-of-function mutations in the
genes encoding CD95 and CD95L, respectively. Both mutations
permit activated T cells to accumulate and accelerate autoimmune

diseases. For example, lpr mice do not express CD95 on their
thymocytes. As a result their thymocytes do not undergo apoptosis
(negative selection), and they escape into the secondary lymphoid
organs. Here they proliferate, resulting in a gross increase in the

size of their lymphoid organs (lymphadenopathy). Many of these
cells respond to self-antigens and lpr mice develop an autoimmune
disease similar to systemic lupus erythematosus (Chapter 38).

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