NK / NKT Cells
Natural Killer (NK) cells are important effector lymphocytes of innate immunity that exhibit cytolytic activity against a variety of allogeneic targets in a non-specific, contact-dependent, nonphagocytic process which does not require prior sensitization to antigen. NK cells share several properties with conventional cytotoxic T cells (CTL), including similar mechanisms for cytolysis. Cytolytic activity is mediated by secretion of pore-forming proteins such as Granzyme B and Perforin, serine proteases and other proteins. NK cytotoxic activity is positively regulated by IL-2, IL-15 and interferons; and is diminished by prostaglandins and TGF-beta.
Natural Killer T (NKT) cells represent a distinct lineage of T cells that express an invariant alpha/beta T cell receptor (TCR) and share a number of cell surface markers in common with NK cells. NKT cells are activated by glycolipid antigens presented by CD1d. Expression of CD160 and Valpha24Jalpha18 TCR can be used for the identification of mouse and human NKT cells, respectively.