NK cell activity in adult infection can protect against HIV disease progression, as shown by immunogenetic studies demonstrating that the combination of Bw4-80I alleles such as HLA-B∗57 with high-expressing KIR3DL1 allotypes enhance the effects of HLA-B∗57 alone in slowing disease progression and improving control of viral load [38]. Here, KIR3DL1 is linked to infection.