Induction of Interleukin‐2 Production in CD4+ and CD8+ T‐Cell Subsets after Activation via CD3 and CD2

The activation signals necessary for interleukin-2 (IL-2) receptor induction, IL-2 production, and DNA synthesis in resting T cells were investigated. IL-2 receptors were induced after activation via CD2 or CD3 alone, while IL-2 production in both CD4+ and CD8+ T cells required activation via both CD3 and CD2. The sequence of activation signals via CD3 and CD2 was shown to be important since DNA synthesis was induced when the primary activation signal was delivered via CD3, and the CD2 signal within 8 h. In contrast, no DNA synthesis was demonstrated when the primary activation signal was delivered via CD2 and the CD3 signal later. Ciclosporin A (CyA) inhibited T-cell DNA synthesis after activation via CD2 and CD3. The inhibition seemed to be due to the prevention of IL-2 synthesis.