title: The human LT serum. X. The initial form released by T-enriched lymphocytes is 150,000 m.w., associated with small nonlytic components, and can dissociate into the smaller alpha, beta, and gamma m.w. classes.
abstract: The present studies examine the various lymphotoxin (LT) forms released in vitro by phytohemagglutinin- (PHA) activated T-enriched (Te) human peripheral blood lymphocytes. It is clear that Te cells rapidly released (24 to 48 hr) these molecules in vitro. The 1st cell-lytic form detected in these supernatants is a 140-160,000 m.w. molecule(s) termed precursor alpha heavy (P alpha H). This form does not express alpha-LT antigenic determinants but is neutralized by antisera from animals injected with serum-free PHA-activated unseparated lymphocyte supernatants (anti-WS). The P alpha H is converted into alpha H, which expresses alpha determinants, by passage through molecular sieving columns or by treatment with low levels of Nonidet P-40 or urea. These treatments dissociate a small nontoxic 10-20,000 m.w. molecule(s), termed precursor factor (Pf), which masks the alpha-LT determinant on the P alpha H molecule. The dissociation of Pf is reversible, since alpha H from the molecular sieving columns will reassociate with the Pf. The alpha H LT class can further dissociate into the smaller alpha, beta, and gamma LT forms upon chromatography on a molecular sieving column, and a certain small percentage of the alpha H forms appear capable of associating to form the high m.w. complex (Cx) LT class. These findings suggest P alpha H may represent an intermediate that requires additional processing in order to proceed down 1 of 2 pathways: a) formation of complexes that are highly cell-lytic, or b) degradation by dissociation into the smaller weakly cell-lytic molecules identified as LT forms.
mesh_terms: D000818:Animals; D000941:Antigens; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D003602:Cytotoxicity, Immunologic; D000939:Epitopes; D006801:Humans; D007106:Immune Sera / Q000494:pharmacology; D007700:Kinetics; D008233:Lymphotoxin-alpha / Q000276:immunology / Q000378:metabolism*; D051379:Mice; D008970:Molecular Weight; D010835:Phytohemagglutinins / Q000494:pharmacology; D012756:Sheep; D013601:T-Lymphocytes / Q000378:metabolism*
chemical_list: D000941:Antigens; D000939:Epitopes; D007106:Immune Sera; D008233:Lymphotoxin-alpha; D010835:Phytohemagglutinins