Naive and memory CD4 and CD8 T cells produce AR. To examine the ability of naive and memory T cell subpopulations to express AR, we stimulated PBMC with an allogeneic EBV-transformed B cell line, which would be expected to activate a small fraction of both memory and naive CD4 and CD8 T cells. Alloantigens stimulated a fraction of both CD4 and CD8 T cells to produce AR ( Figure 4A ), relative to the unstimulated control. The specificity of staining was confirmed by isotype control antibodies. The cells producing AR (and other cytokines) were included in the CD69+ population.