title: Detection of proteolytic (C 3-cleaving) activity on mouse mastocytoma (P 815) cells and other mouse cell lines by formation of cell contact with C 3-carrying mouse lymphocytes.
abstract: Mouse mastocytoma cells (P 815) formed rosettes with normal mouse spleen lymphocytes which had been coated with uncleaved human C 3; this interaction was clearly dependent on the amount of C 3. Lymphocytes treated with C 3 b or buffer alone were ineffective. Formation of cell contact could be inhibited by the presence of protease inhibitors such as diisopropyl fluorophosphate, phenyl methyl sulfonyl fluoride and tosyllysyl chloromethyl ketone. Seve n out of 13 different cell lines behaved like P 815 cells. The results strongly suggested that a proteolytic activity on mouse tumor cells led to a cooperation with uncleaved C 3 on a carrier cell to connect these two cells. We interpreted these data in analogy to the complement-dependent bridge formation mechanism (M. P. Dierich and B. Landen, J. Exp. Med. 1977. 146: 1484): uncleaved C 3, attached to mouse spleen lymphocytes as carriers, becomes cleaved by enzymes associated with the tumor cells tested; by this cleavage, the labile binding site is released on C 3 (nascent C 3 b) and anchors the C 3-carrying cell to the protease-carrying cell; since this labile binding site is short-lived, this process can be induced by membrane-associated proteases only. The nature of the proteases and the biological implications of this process are as yet uncertain.
mesh_terms: D000818:Animals; D002452:Cell Count; D002460:Cell Line; D002462:Cell Membrane / Q000201:enzymology / Q000276:immunology; D003176:Complement C3 / Q000276:immunology* / Q000494:pharmacology; D008214:Lymphocytes / Q000276:immunology*; D012515:Mast-Cell Sarcoma / Q000201:enzymology / Q000276:immunology*; D051379:Mice; D011480:Protease Inhibitors / Q000276:immunology / Q000494:pharmacology; D012397:Rosette Formation; D013154:Spleen / Q000166:cytology
chemical_list: D003176:Complement C3; D011480:Protease Inhibitors