In vitro lymphocyte cytotoxicity II. Unstable lymphotoxins (β-LT) secreted and inactivated by mitogen-stimulated human lymphocytes

Abstract

Supernatants from phytohemagglutinin (PHA)-activated human lymphocytes contain two major classes of cytotoxins (α-LT and β-LT). While α-LT appears to be stable, and the major component in 5-day culture supernatants, the majority of cytolytic activity at earlier intervals in these cultures is due to a “family” of highly unstable cytotoxins which are both secreted and destroyed at a rapid rate. The inactivation of the unstable LT molecules appears to be due to: (a) inherent instability o β-LT molecules, and (b) a lymphocyte-mediated inactivation mechanism(s) which involves serum.