IL-7 and homeostasis of recent thymic emigrants

By contrast, conditions that induce lymphopenia, such as infection with HIV, toxic agents, irradiation and cytotoxic drugs, result in spontaneous homeostatic proliferation to restore the size of the T-cell pool, and this process can be independent of the thymus. Homeostasis of CD8+ T cells in the presence of low-affinity peptides or self-antigens does not induce the expression of these activation markers either, although cells do acquire a memory phenotype (CD44hi), up-regulate their expression of CD122 and CD132, and have significant effector function (cytotoxic activity and production of interferon γ) [6-8].