Specific and non-specific immunologic mechanisms of tumor growth facilitation

Specific and non-specific mechanisms of tumor growth facilitation were studied using methylcholanthrene (MCA)-induced fibrosarcomas in C3H/HeJ mice. In early and late stages of tumor growth, mice possessed non-specific, tumor-facilitating cells detected by local adoptive transfer assay (LATA). These cells appeared to be macrophages; they were radioresistant (700 rads), phagocytic, and adherent to plastic. Specific tumor facilitation was induced by treatment either with crude 3M KCl extracts, or with an acidic pIEF fraction (pI 3.5). After treatment with this material, animals displayed facilitated outgrowth of only MCA-F, but not the antigenically distinct MCA-D or MCA-C tumors. Thus in addition to non-specific stimuli, which accelerate neoplastic growth, tumors bear tumor-specific transplantation antigens (TSTA), which induce specific facilitation.