CD45RA-expressing memory/effector Th cells committed to production of interferon- γ lack expression of CD31

Abstract

It has been considered before that human naive and memory/effector CD4 + T-cells cannot be subdivided solely according to the differential expression of CD45 isoforms. By the lack of expression of CD31 we have identified a subset of CD4 + CD45RA + CD31 − cells which show distinct features of antigen-experienced Th1 cells. Short term stimulation of highly purified human peripheral blood CD4 + T-cells with PMA/ionomycin, followed by the cytometric analysis of intracellular cytokines, showed that a minor subpopulation of CD4 + CD45RA + CD45RO − cells is able to produce interferon- γ (IFN- γ) rapidly, a characteristic of antigen-experienced Th1 cells. Whereas among CD45RA + CD4 + T-cells both CD31 + and CD31 − subsets produce interleukin-2 (IL-2) upon PMA/ionomycin stimulation, only the CD31 − subpopulation is able to produce IFN- γ. Thus, our phenotypic and functional characterization of CD45RA + CD45RO − Th cells shows that CD45RA + CD45RO − cells do not represent a homogeneous population of antigen-unexperienced, naive T-cells. We speculate that a certain subset of human CD4 +, CD45RO + memory T-cells reverts to expression of the CD45RA isoform, and that this subset can be identified by the lack of CD31 expression.