111 MEMBERS OF THE CYTOKINE-RECEPTOR GAMMA-CHAIN CYTOKINE FAMILY REGULATE CD8+CD127+ AND CD8+CD127-T-CELL CYCLING, SURVIVAL AND SUSCEPTIBILITY TO ACTIVATION-INDUCED APOPTOSIS A Crawley1, T Katz2, K Parato1, J Angel1 Objectives: The expression of IL-7 receptor alpha (CD127) on CD8+ T-cells has been associated with HIV pathogenesis and is down-regulated by cytokines of the cytokine-receptor gamma-chain cytokine family (IL-2,-4,-7,-15,-21), as shown previously in this lab. These cytokines influence T-cell differentiation, although the importance of CD127 in the process is unknown. This research investigates how this family of cytokines contributes to the maintenance, survival and differentiation of CD8+ T-cells in the context of CD127 expression.
1Ottawa Health Research Institute; 2University of Ottawa, Ottawa, Ontario
Methods: Cell division of isolated CD8+CD127+ and CD8+CD127-T-cells in response to mitogenic stimuli and cytokines was analyzed by flow cytometry using CFSE. The expression of CD45RA was used to distinguish between naïve, effector and memory cells. Expression of anti-apoptotic bcl-2 in cytokine-treated cells was assessed and susceptibility to apoptosis-inducing stimuli (anti-Fas or anti-CD3) was measured by AnnexinV+ cell staining.
Results: A significant increase in the percentage of activated CD127+CD45RA-and CD127-CD45RA-cells (effector/memory) undergoing multiple cell divisions in response to mitogen and IL-4 was observed compared to CD127+CD45RA+ and CD127-CD45RA+ cells (naïve/effector). This effect was especially pronounced in the CD127-population. The expression of bcl-2 in IL-2- or IL-15-treated CD8+CD127+ T-cells was significantly greater than that in CD8+CD127- T-cells. Preliminary results suggest that Fas expression influences responses to activation-induce apoptosis.
Conclusions: This research is the first to treat isolated CD8+CD127+ and CD8+CD127-T-cells with cytokines and the results suggest subset-specific responses. Differences in cell division potentials and susceptibility to apoptosis between these subsets may explain cell fate determination. For instance, the CD8+ T-cell effector phase is followed by significant cell death and the generation of memory CD8+ T-cells expressing high levels of CD127. Identifying novel aspects of CD127 T-cell subsets will contribute to the design of therapies aimed at enhancing CD8+ T-cell function and controlling HIV viral replication as well as add to the knowledge base relating to T-cell homeostasis.