ABSTRACT

The immune system has evolved to combat infectious organisms through the coordination of both innate and acquired immune responses. Innate immune responses generally pass their roles in eradicating pathogens to acquired immune responses conducted by T and B cells. T and B cells generate diverse antigen-specific receptors through gene recombination, and both cell repertoires are shaped during their development by recognizing self-antigens. After cell maturation, the repertoire selection is further developed by recognizing non—self-antigens, which is essential for efficient eradication of pathogens. Those antigen-driven selections are seen not only in conventional CD4⁺ and CD8⁺ T cells but also in CD4⁺CD25⁺ regulatory T cells. In this article, we review current concepts of repertoire selection of conventional T cells, as well as regulatory T cells, and discuss the physiological role of such selection in controlling acquired immune responses against pathogens.