CD8+ Regulatory cells

Regulatory T cells are heterogeneous with sub-populations which differ from each other in their phenotype, immune inhibitory mechanisms and functioning. These cells are responsible for regulation of immune response and play a leading role in developing immune tolerance through active suppression. Suggested functions for regulatory T cells include: prevention of autoimmune diseases by maintaining self-tolerance, oral tolerance and, moreover, suppression of allergy and pathogen-induced immunopathology. CD4(+) regulatory cells, such as Treg, Tr1 and Th3, are the most comprehensively studied and characterized regulatory lymphocytes; however, in recent years substantial progress has been made in the phenotypic and functional characterization of CD8(+) regulatory cells. These cells can be divided into two general groups: natural and induced lymphocytes. Natural regulatory cells develop in the thymus, constitute a stable lineage, while their induced counterparts are generated under experimental conditions and may or may not have stable phenotypes. Both types of these cells can be subdivided into several phenotypic groups. The author reviews the current state of knowledge concerning the best-characterized human and murine CD8(+) regulatory lymphocytes, i.e., CD8(+)CD25(+)Foxp3(+), CD8(+)Foxp3(+), CD8(+)CD122(+) and CD8(+)CD28(-) cells. This paper focuses on aspects concerning the phenotype and phenotypic markers of these cells, as well as their immune inhibitory mechanisms.