Complement-dependent in vitro cytotoxicity against autologous invasive bladder tumor cells in humans. Evaluation of the possible role of naturally-occurring antibodies in complement-dependent cytotoxicity.

Complement-dependent serum-mediated cytotoxicity (CDC) was measured in a 51-chromium release assay against autologous tumor cells from 7 non-invasive and 9 invasive transitional-cell tumors of the urinary bladder. CDC was demonstrated against tumor cells from invasive tumors. Heat-inactivation of autologous sera lead to complete loss of cytotoxicity. There were no differences in CDC of autologous sera from patients and allogenic sera from controls. The cytotoxic response seems to be strongly dependent on the target cell. CDC was significantly reduced by use of an allogenic C 2 deficient serum. Direct immunofluorescence did not reveal any tumor cell associated immunoglobulins of IgG or IgM classes. Indirect immunofluorescence with autologous heat-inactivated sera demonstrated in most cases both IgG and IgM attachment to the tumor cells, but there were no obvious relations between indirect immunofluorescence and CDC. Absorption of allogenic sera to trypsin- or neuraminidase-treated erythrocytes did not affect CDC of these sera against invasive tumor targets. The results indicate a complement-dependent cytotoxicity against target cells from invasive bladder tumors. Complement seems to be activated through the classical pathway, but the possible role of naturally-occurring antibodies against invasive tumor targets is not clarified.