Coexistence of autologous antibodies and decay-accelerating factor, an inhibitor of complement, on human renal tumor cells.

Autologous immunoglobulin was detected on the cell surface of tumor cells freshly isolated from cancerous kidneys of patients with renal cell carcinoma by flow cytometry after staining with murine anti-human IgG monoclonal antibodies. Cells isolated in parallel from macroscopically normal regions of the tumorous kidneys were not specifically stained with the anti-human IgG reagents. In further studies, tumor cells were stained with an antibody to decay-accelerating factor (DAF), a known inhibitor of complement. Flow cytometry of these cells revealed that nearly all tumor cells expressed DAF, and that the intensity of staining with the anti-DAF monoclonal antibody correlated with the staining of cells with anti-IgG. The results suggest that tumor cells coated with autologous antibody may be resistant to complement-mediated cytotoxicity in vivo through the expression of high levels of DAF.