Gamma interferon is a major suppressive factor produced by activated humanperipheral blood lymphocytes that is able to inhibit foamy virus-induced cytopathic effects

The activation of human peripheral blood lymphocytes by mitogens or by trig gering the T-cell receptor with anti-CD3 antibodies leads to the production of a potent soluble inhibitory activity against foamy virus-induced cytopa thic effects in vitro. The inhibitory activity acts in a species-specific m anner. As a consequence, the isolation of foamy viruses from blood lymphocy tes of infected humans is accelerated in a heterologous coculture system. A ntibodies against gamma interferon (IFN-gamma) are able to suppress most of the inhibitory activity, suggesting that IFN-gamma is the dominant compone nt.