The murine Ly49 family: form and function

The activity of natural killer (NK) cells is regulated by surface receptors that recognize class I MHC. Murine NK cells express a large family of lectin-related receptors (Ly49s) to perform this function, while human NK cells utilize a separate group of proteins containing Ig-related domains (KIRs). Although these receptor families are not structurally related, the Ly49 family appears to be the functional equivalent of human KIRs, since it uses similar signal transduction pathways for either activation or inhibition of NK cell function. Therefore, lessons learned from the study of the murine MHC class I receptor system may be relevant to human NK function. This review summarizes the current state of knowledge of the Ly49 family.