What are Positive Signals (Killer Activation Receptors (KARs)?

Involved in positive signaling e.g NKG2D receptor. Recognizes HLA-like molecules (MIC A and MIC B) expressed on stressed or dying cells or virus-infected cells but not normal cells. Fc receptor (CD16). Recognizes Fc region of antibodies. When antibodies are bound to cellular targets, NK cells bind to these antibodies and kill the cellular targets - this process known as antibody-dependent cellular cytotoxicity (ADCC).