What are Killer cell Immunoglobulin-like Receptors KIRs?

Involved in negative signaling Killer cell Immunoglobulin-like Receptors (KIRs) e.g. CD94 + NKG2. Receptors sense normal MHC molecules on healthy cells causing NK cells to shut off. If virus shuts off MHC expression to evade cytotoxic T cells, NK cells will notice MHC is missing and if activation signals are present, NK cell will be activated and cell is killed – “Recognition of Missing Self”