Abstract
The phenotypic activation of T cells is a critical factor for successful adoptive immunotherapy. Typically, activation of T cells coincides with decrease in the expression of the trafficking molecules in particular CD62L. However, sustaining CD62L is beneficial for trafficking of adoptive transferred cells. The aim of the present study was to define the immunomodulatory factors that can increase survival and sustain CD62L expression in antigen-specific T cells. To this end, the effects of interleukin (IL)-2, IL-12, IL-15, insulin-like growth factor-1 (IGF-1), thymosin-α1 (T-α1) as well as all-trans retinoid acid (ATRA) alone or in combination were tested in vitro utilizing OT1 transgenic T cells as a model. The results showed that stimulation of OT1 cells with antigen resulted in a significant activation of these cells as evidenced by the decrease in surface expression of CD62L, analyzed 3 days after antigen stimulation and was more pronounced on day 5. Addition of cytokines (IL-2, IL-12 or IL-15), IGF-1 alone or in combination with cytokines as well as T-α1 alone or in combination with cytokines during antigen stimulation had no effect on the activation profile of these cells 3 days post stimulation. However, they expressed effects on day 5. IL-12 alone, but not IL-2, IL-15, or IGF-1 alone augmented the activation of OT1 cells. Combination of IL-2 or IL-15 with IGF-1 or T-α1 had no further effect. Interestingly, however, combination of IL-12 with IGF-1 sustained the expression of CD62L on OT1 cells. Although addition of ATRA alone or in combination with IL-12 to antigen-stimulated cells resulted in decreases in CD62L expression on day 3, they showed a dose-dependent effect on the restoration of CD62L expression on day 5. Analysis of the activation-induced cell death (apoptosis) of OT1 cells showed more death on day 5 than on day 3-post antigen stimulation. Addition of only IL-12 or IGF-1 alone, but not IL-2, IL-15 or T-α1, decreased OT1 cell apoptosis on day 3. These anti-apoptotic effects of IL-12 and IGF-1, however, were recovered on day 5-post stimulation. In conclusion, these results indicate that the activation phenotype and the survival of antigen-specific T cells can be differentially modulated by different immunomodulatory factors, where, interleukin-12 and IGF-1 induced the favorable effect. These results have a significant implication for T cell adoptive immunotherapy in different settings

Key words: CD8+ T cells, CD62L, IL-2, IL-12, IL-15, IGF-1, T-α1, ATRA, OT-1