Human lymphotoxin obtained from established lymphoid lines: purification characteristics and inhibition by anti immunoglobulin

Human lymphotoxin obtained from established lymphoid cell lines (HLTLCL) was studied in detail and purified using ammonium sulfate fractionation, gel filtration, ion exchange column chromatography, and polyacrylamide gel electrophoresis. HLTLCL is stable at 20°C for over 1 yr, at 4°C for 3 wk, and a 37°C for 1 wk. HLTLCL showed a decrease in activity at pH 2.0 and 3.0, but was stable at a pH range of 5.0-11.0. HLTLCL, which contained fetal calf serum, was purified 50 fold. HLTLCL obtained from serum free culture medium yielded greater purity, although complete purification was not achieved. Antiserum to HLTLCL neutralized the cytotoxic activity of HLTLCL, HLT induced by phytohemagglutinin (PHA) (HLTPHA), and HLT induced by tuberculin purified protein derivative (PPD) (HLTPPD). Antiserum to human IgG, λ type L chain, and Fc fragment partially but significantly inhibited HLTLCL activity. These data, together with previous reports, indicate that the HLTLCL molecule is immunologically similar to HLTPHA and HLTPPD and suggest that there is immunologic cross reactivity with IgG globulin.