Natural killer cell

Abbreviated as NK-cell. A cytotoxic lymphoid cell that is part of the innate immune system. It's cytotoxicity is due to it's ability of releasing small cytotoxic granules such as perforin and granzymes. They have some similarities to the Cytotoxic CD8+ T-cells. However, unlike the T-cells, NK-cells do not express T-cell Receptors (TCRs), surface CD3 or CD5. They usually express CD56, CD16 and contain some relatively NK specific receptors such as CD94 and KIR (Killer-cell Immunoglobulin-like Receptor).