Differential expression of CD300a/c on human TH1 and TH17 cells.

Human memory CD4+ T cells can be either CD300a/c+ or CD300a/c- and subsequent analyses showed that CD4+ effector memory T (T(EM)) cells are mostly CD300a/c+, whereas CD4+ central memory T (T(CM)) cells have similar frequencies of CD300a/c+ and CD300a/c- cells. Extensive phenotypical and functional characterization showed that in both T(CM) and T(EM) cells, the CD300a/c+ subset contained a higher number of TH1 (IFN-γ producing) cells. Alternatively, TH17 (IL-17a producing) cells tend to be CD300a/c-, especially in the T(EM) subset. Further characterization of the IL-17a+ cells showed that cells that produce only this cytokine are mostly CD300a/c-, while cells that produce IL-17a in combination with other cytokines, especially IFN-γ, are mostly CD300a/c+, indicating that the expression of this receptor is associated with cells that produce IFN-γ. Co-ligation of the TCR and CD300a/c in CD4+ T cells inhibited Ca2+ mobilization evoked by TCR ligation alone and modulated IFN-γ production on TH1 polarized cells. We conclude that the CD300a/c receptors are differentially expressed on human TH1 and TH17 cells and that their ligation is capable of modulating TCR mediated signals.