title: Serine esterase in cytolytic T lymphocytes.
abstract: The mechanisms that enable cytotoxic T lymphocytes (Tc cells) to destroy target cells are only vaguely understood. However, recent studies have identified in Tc cells and natural killer cells cytoplasmic granules that contain perforin, a cytolytic protein that resembles the ninth component of complement (C9). Antigen-specific lysis of target cells, traditionally ascribed solely to Tc cells, has now also been demonstrated in some T-helper cell (Th cell) lines, referred to here as T helper-killer or Th/c cells. We recently found a novel serine esterase that is present at greatly elevated levels in cloned murine Tc cell lines and one Th/c cell line, but not in two non-cytolytic Th cell lines. These findings suggest that the serine esterase is involved in cytolytic activity and that a variety of effector cells share a common cytolytic mechanism. To explore the role of the serine esterase in this process, we have been studying additional properties of the enzyme in murine T cells. We show here that it is a membrane-associated, disulphide-linked dimer, it has trypsin-like properties but is not a general protease, in density gradient centrifugation it sediments with perforin, it is secreted by Tc cells during their cytolytic attack on target cells, and antiserum to Tc-cell serine esterase reacts with the enzyme in Th/c cells.
mesh_terms: D000818:Animals; D002460:Cell Line; D003602:Cytotoxicity, Immunologic; D004950:Esterases / Q000302:isolation & purification*; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000032:analysis / Q000302:isolation & purification; D051379:Mice; D054353:Perforin; D052899:Pore Forming Cytotoxic Proteins; D013602:T-Lymphocytes, Cytotoxic / Q000201:enzymology* / Q000276:immunology
chemical_list: D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D052899:Pore Forming Cytotoxic Proteins; D054353:Perforin; D004950:Esterases; C022635:serine esterase