Phenotype and Functional Characteristics of Human Post Thymic Maturation T Cell Subsets

Publisher Summary Phenotypically distinct maturational subsets of peripheral blood T lymphocytes have been identified in humans. These reciprocal subsets are distinguished by different levels of expression of several different cell surface molecules and a variety of functional differences in activation responses, lymphokine secretion, and adhesion properties. These subsets are understood to represent post-thymic T cells that have never been activated and that express high levels of CD45RA and T cells that have undergone postthymic activation, losing expression of CD45RA and acquiring high levels of expression of other molecules including, LFA-1, CD2, LFA-3, CD45R0, and CDw29. Unprimed, or naive, T cells are contained in the first subset, while antigen primed or memory T-cells are contained in the second subset. Although it is possible that activation and phenotypic conversion could occur in vivo by some mechanism other than exposure to specific antigen, it can be hypothesized that antigen-specific activation accounts for most of the conversion, and employ the terms memory and naive throughout this review to refer to these subsets