Human CD8 T cells of the peripheral blood contain a low CD8 expressing cytotoxic/effector subpopulation

摘要

Heterogeneity of lymphocyte populations demonstrates the diversity of cellular immune responses and provide a better understanding of the immune system. CD3⁺ CD8⁺ T cells exhibit a low CD8 expressing (CD8^low) population in flow cytometric analysis of peripheral blood T cells. In healthy donors, this population consists of 0·2–7·0% of all CD8 T cells. The majority of the CD8^low T cell population showed an elevated expression of CD25, CD45RA, and CD95L, and low levels of CD28, CD62L and CD45RO. Circulating CD8^low T cells resemble cytotoxic effector cells because they express cytolytic mediators and are able to execute cytotoxicity. A restricted T cell receptor profile with increased Vβ9, Vβ14 and Vβ23 expression was observed and the CD8^low T cell population contain Epstein–Barr virus-specific T cells. Therefore, the CD8^low population represent a subset of activated CD8 effector T cells, resulting most probably from a continous and/or balanced immune response to intracellular pathogens.