Page 426 - Veterinary Immunology, 10th Edition

VetBooks.ir

FIG. 14.22 Following T cell-DC interactions, the T cell divides
asymmetrically. The cell at the pole in contact with the antigen-
presenting dendritic cell synapse becomes a helper T cell. The cell
at the opposite pole receives different signals and so becomes a
memory T cell.

Three types of memory T cells have been characterized. These are
central memory cells, tissue-resident memory T cells, and effector

memory T cells. Central memory T cells circulate through
secondary lymphoid tissues, such as lymph nodes, awaiting the
arrival of invaders. They lack immediate effector function but have
very rapid recall responses. Effector memory T cells, in contrast,

have receptors enabling them to hone to inflamed tissues, where
they immediately attack invaders without the need to differentiate
further. Tissue-resident memory T cells occupy tissues and provide
a first response to pathogens invading through body surfaces. They

rapidly produce cytokines after infection. They do not circulate in
peripheral blood. All memory T cell populations express either CD4
+
or CD8 and persist in the absence of antigen. CD8 memory cells

426