The existence of helper cells among the CD8+ T cell subset has been recognized for a long time. However, the phenotype of these cells has remained elusive. In this study, we provide evidence that the expression of the CDw60 antigen on human CD8+ T cell allows one to distinguish between CD8+ T helper cells and CD8+ T cells with cytotoxic and suppressor capacity. CDw60 monoclonal antibodies (mAb) recognize the 9-O-acetylated disialosyl group on ganglioside GD3 expressed on 20-40% of CD8+ cells. By use of the direct and indirect mAb-rosetting technique, we were able to isolate the CDw60+CD8+ and CDw60-CD8+ cells at high purity. The alloantigen-specific cytotoxic activity of CD8+ cells resided entirely in the CDw60- population. Helper and suppressor capacity of both CD8 subsets was assayed by the pokeweed mitogen-induced differentiation of B cells into immunoglobulin-secreting cells. These studies clearly indicate that the CDw60+CD8+ subset provided substantial help to B lymphocytes, whereas the CD8+ cells with the CDw60- phenotype were suppressing B cell differentiation. Both subsets produced similar amounts of interleukin 2 (IL-2) after stimulation with phytohemagglutinin. Activation with phorbol myristate acetate in combination with Ca-ionophore induced IL-4 secretion in both populations, but preferentially in the CDw60+ subset, whereas the vast majority of interferon gamma was produced by the CDw60-CD8+ cells. When used in combination with other markers, CDw60 may prove to be useful in defining CD8+ subsets with reciprocal functional activities.

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