Induction of CD69 antigen on normal CD4(+) and CD8(+) lymphocyte subsets and its relationship with the phenotype of responding T-cells

We evaluated phenotype and apoptotic status of normal CD4(+)CD69(+) and CD8 (+)GD69(+) peripheral blood T-lymphocytes after short-term challenge with e scalating concentrations of phytohemagglutinin (PHA), The frequency of CD69 -coexpressing CD4(+) and CD8(+) T-cells and CD69 staining intensity increas ed following T-cell mitogenic stimulation; these changes were proportional to PHA concentration in culture medium. A considerable fraction of lymphocy tes underwent blast transformation, displaying increased forward and side s catter signals. interestingly enough, PHA-responsive T-cells exhibited a pr edominantly CD25(neg)CD38(neg)TCR alpha beta(pos) phenotype; APO-1/Fas anti gen (CD95) could be detected on a minority of activated CD69(+) T-cells, A considerable proportion of CD69(+) lymphocytes expressed intracellular perf orin; in addition, an average 16 +/- 6% CD69(+) T-lymphocytes were apoptoti c after 4 h of stimulation, as evaluated by 7-amino-actinomycin-D staining and by annexin-V binding, CD69(+) activated lymphocytes comprise phenotypic ally heterogeneous cell subpopulations potentially devoted to diverse immun ological functions, i.e., proliferation, apoptosis, or cell cytotoxicity; m oreover, our findings indicate that CD69 expression is proportional to the intensity of the activating stimulus and that the capacity to upregulate CD 69 antigen following short-term mitogenic challenge may be restricted to un activated CD38(neg)CD25(neg)TCR alpha beta(pos) T-lymphocytes. (C) 1999 Wil ey-Liss, Inc.