Faculty Bibliography

Purified natural and recombinant human immune interferon (IFN-gamma) were found to activate human monocytes from peripheral blood to exert enhanced cytotoxicity against human colon adenocarcinoma HT-29 cells. A marked monocyte activation was observed at low concentrations (1 and 10 U/ml) of IFN-gamma. Marked monocyte activation was also obtained with two lymphokine preparations, produced in peripheral blood mononuclear cell (PBM) cultures induced with phytohemagglutinin (PHA) or by combined stimulation with PHA and 12-O-tetradecanoylphorbol 13-acetate (TPA). The component responsible for macrophage activation in such lymphokine preparations in the past was considered to be 'macrophage-activating factor' (MAF). When monoclonal antibody specifically neutralizing IFN-gamma was added to these lymphokine preparations, all MAF activity disappeared, indicating that IFN-gamma is the sole protein showing MAF activity in these preparations

Two IgG1/kappa class monoclonal antibodies specific for human immune interferon (IFN-gamma), designated B1 and B3, were developed. Specific binding of both monoclonal antibodies to natural or Escherichia coli-derived recombinant human IFN-gamma was demonstrated in a solid-phase radioimmunoassay or by immunoprecipitation. Antibody B3 showed potent neutralizing activity against both natural and recombinant IFN-gamma. Antibody B1, which showed neutralizing activity only when very high concentrations were employed, was used for preparing immunosorbents for affinity chromatography of IFN-gamma. When a highly purified preparation of 125I-labeled natural IFN-gamma was loaded onto the affinity column, all of the biological activity was retained on the column. The bulk of 125I-labeled IFN-gamma bound to the affinity column be eluted in biologically active form, suggesting that antibody B1 could be used for the purification of human IFN-gamma. Analysis of IFN-gamma eluted from the column by NaDodSO4/polyacrylamide gel electrophoresis (SDS-PAGE) indicated that both of the known molecular weight subspecies of IFN-gamma (25,000 and 20,000 MW), as well as the presumed dimer of 45,000 MW, were retained by the B1 antibody affinity column

Previous studies showed that the tumor-promoting phorbol ester 12-O-tetradecanoylphorbol 13-acetate (TPA) and several structurally related tumor-promoting compounds stimulate lymphocytes to produce immune interferon (IFN-gamma) and interleukin 2 (IL-2). This study shows that three compounds structurally unrelated to TPA, previously shown to mimic TPA in some other biological activities, are similar to TPA in stimulating IFN-gamma and Il-2 production in cultures of human peripheral blood lymphocytes. The production of another lymphokine, termed lymphotoxin (LT), was also enhanced by TPA and the other three compounds examined. Maximal enhancement of lymphokine production was observed in cultures costimulated with TPA or one of the other tested compounds and phytohemagglutinin (PHA). TPA was separated from IFN-gamma during a multistep purification procedure