Histopathology of Tumor Regression After Intralesional Injection of Mycobacferium bovis . IV. Development of Immunity to Tumor Cells and BCG 2

Abstract

Transplanted syngeneic tumors established in the skin of inbred guinea pigs regressed and regional metastases were eliminated after intralesional injection of Mycobacterium bovis strain bacillus CalmetteGuerin (BCG). Specific immunity to tumor cells and BCG was evaluated in this therapy model. The results demonstrated that BCG-mediated regression of established tumors had both local and systemic features, both of which involved host-specific immunity. Early sensitization to BCG antigens was required in guinea pigs whose peripheral and central lymphocyte compartments were depleted as a result of pretreatment with antilymphocyte serum. The ability to develop delayed sensitivity to a purified protein derivative of BCG was correlated with tumor regression after injection of BCG into established tumors. The development of specific tumor immunity was an aspect of this experimental model. Guinea pigs with established tumors developed humoral and cell-mediated immunity during BCG-mediated tumor regression. Anti60dy with specificity for line-10 tumor cells was demonstrated by the positive immunofluorescence and C1 fixation and transfer tests of plasma from BCG-treated, tumor-bearing guinea pigs. Systemic cell-mediated immunity was shown by the classic lymphocyte-mediated rejection of line-10 tumor challenge in guinea pigs that had undergone BCG-mediated regression of line-10 tumors.