CD8 T cells express randomly selected KIRs with distinct specificities compared with NK cells

Epistatic interactions between killer cell immunoglobulin-like receptors (KIRs) and their cognate HLA class I ligands have important implications for reproductive success, antiviral immunity, susceptibility to autoimmune conditions and cancer, as well as for graft-versus-leukemia reactions in settings of allogeneic stem cell transplantation. Although CD8 T cells are known to acquire KIRs when maturing from naive to terminally differentiated cells, little information is available about the constitution of KIR repertoires on human CD8 T cells. Here, we have performed a high-resolution analysis of KIR expression on CD8 T cells. The results show that most CD8 T cells possess a restricted KIR expression pattern, often dominated by a single activating or inhibitory KIR. Furthermore, the expression of KIR, and its modulation of CD8 T-cell function, was independent of expression of self-HLA class I ligands. Finally, despite similarities in the stochastic regulation of KIRs by the bidirectional proximal promoter, the specificity of inhibitory KIRs on CD8 T cells was often distinct from that of natural killer cells in the same individual. The results provide new insight into the formation of KIR repertoires on human T cells.