Induction of tumor-cell lysis by bi-specific monoclonal antibodies recognizing renal-cell carcinoma and CD3 antigen.

Bi-specific monoclonal antibodies (MAbs) were developed by somatic hybridization of 2 mouse hybridomas, one producing MAb against the G250 renal-cell carcinoma (RCC)-associated antigen and the other against the T-cell antigen CD3 (OKT3). The dual specificity of the hybrid MAb produced by these so-called quadromas was analyzed by immunohisto chemistry on tissue sections and by cytotoxicity assays with relevant target and effector cells. The bi-specific MAb could induce TCRαβ/CD3+ and TCRγδ/CD3+ cloned lymphocytes to kill RCC cells. A noteworthy finding was that the TCRαβ and γδ lymphocyte clones showed different triggering abilities. The specificity of target-cell lysis by the cytotoxic T cells (CTL) was dictated by the specificity of the G250 MAb. Control bi-specific MAb, recognizing a cell-surface structure not involved in T-cell activation, did not induce lysis. Several lgG subclass switch variants of the G250 hybridoma, i.e., lgG1, 2a, and lgE, were used for somatic hybridization with the OKT3 hybridoma (lgG2a. Except for lgE, all lgG subclass combinations could equally induce cytolysis. Induction of cytolysis was inhibited only by excess OKT3 MAb. Comparison of 2 bi-specific MAb preparations of the same combination (lgG2a/1), produced by 2 quadromas derived from the same parental hybridomas after identical purification procedures, produced different amounts of bispecific MAb.