Identification and Enrichment of Proteolytic Enzymes of IL-2 Activated Rat Natural Killer (A-NK) Cells: Potential Physiological Roles in NK Cell Function

Proteolytic enzymes, implicated to play a potential role in cell-mediated cytotoxicity, have been focused upon in many investigations of cytolytic T cells, Natural Killer (NK) cells and lymphokine activated killer (LAK) cells. The observation that large granular lymphocytes (LGL) account for NK cell activity and that LGL can be enriched to a high degree of purity have allowed for the use of enriched populations of NK cells for biochemical studies. The granzymes are the most widely examined of these killer cell-associated proteolytic enzymes. This collection of neutral, serine proteases are found in the cytolytic granules of cloned, murine cytolytic T-cells. Proteases have also been discovered in the lytic granules of human, cloned cytotoxic T-cells, rat NK cells lines and LAK cells from both human and murine sources. The biochemical properties of A-NKP-1 and A-NKP-2 coupled with their high molecular weight and substrate specificities led us to consider that this protease complex was related to multicatalytic proteinase complex.