Immunologic Enhancement of Tumor Xenografts by Pepsin-Degraded Immunoglobulin

Abstract

The serums from guinea pigs previously injected with mouse Ehrlich ascites tumor cells were fractionated to obtain γ₂-immunoglobulin. This immunoglobulin was degraded with pepsin to obtain an F(ab')₂ fragment. Fresh tumor cells were incubated with immunoglobulin or the fragment and injected into normal guinea pigs. The growth of these cells as tumor xenografts was inhibited by the γ₂-immunoglobulin and enhanced by the F(ab')₂ fragment. Similar incubation of tumor cells with normal guinea pig γ₂-globulin or its derived F(ab')₂ fragment did not alter subsequent tumor growth.