Expression of IL‐15RA or an IL‐15/IL‐15RA fusion on CD8+ T cells modifies adoptively transferred T‐cell function in cis

Abstract IL‐15 and IL‐15 receptor alpha (IL‐15RA) play a significant role in multiple aspects of T‐cell biology. However, given the evidence that IL‐15RA can present IL‐15 in trans , the functional capacity of IL‐15RA expressed on CD8 + T cells to modify IL‐15 functions in cis is currently unclear. In the current study, we explore the functional consequences of IL‐15RA, expression on T cells using a novel method to transfect naive CD8 + T cells. We observed that RNA nucleofection led to highly efficient, non‐toxic, and rapid manipulation of protein expression levels in unstimulated CD8 + T cells. We found that transfection of unstimulated CD8 + T cells with IL‐15RA RNA led to enhanced viability of CD8 + T cells in response to IL‐15. Transfection with IL‐15RA enhanced IL‐15‐mediated phosphorylation of STAT5 and also promoted IL‐15‐mediated proliferation in vivo of adoptively transferred naïve CD8 + T cells. We demonstrated that IL‐15RA can present IL‐15 via cis ‐presentation on CD8 + T cells. Finally, we showed that transfection with a chimeric construct linking IL‐15 to IL‐15RA cell autonomously enhances the viability and proliferation of primary CD8 + T cells and cytotoxic potential of antigen‐specific CD8 + T cells. The clinical implications of the current study are discussed.