Inhibitory KIR/HLA incompatibility between sexual partners confers protection against HIV-1 transmission.

Killer immunoglobulin-like receptors (KIRs) regulate natural killer (NK) cells in a human leukocyte antigen (HLA)-dependent manner. KIR/HLA mismatched hematopoietic stem cell transplants induce alloreactive NK cells, which prevent leukemia relapse. Certain KIR/HLA combinations protect against HIV-1 infection, but the effect of KIR/HLA mismatches between sexual partners has never been investigated.