In vitro reversal of depressed T-lymphocyte function in the peripheral blood of brain tumor patients.

Peripheral blood mononuclear cells from some brain tumor patients exhibited depressed T-lymphocyte responses to the polyclonal mitogen phytohemagglutinin (PHA). These responses, initially depressed, were restored to near normal by a 24-hour preculture in growth medium. The effect of preculture was mimicked by mild trypsinization before addition of PHA. In addition, cells treated with deaggregated antihuman IgG resulted in greatly reduced responses to mitogen by mononuclear cells from all brain tumor patients. Anti-IgG had no effect if cells were precultured for 24 hours. The results suggest that, in brain tumor patients, depressed immune function associated with tumor progression was caused by suppressor cells which were activated by humoral factors that express IgG antigenic determinants.