Activation of homologous complement via the alternative complement pathway by quail cells transformed by Rous sarcoma virus

After incubation of the cells with fresh quail serum, deposition of the third component of complement (C3) was demonstrated on the cell surface of various quail cell lines transformed by Rous sarcoma virus (RSV) as well as on that of primary quail embryo (QE) cells transformed by RSV. The C3 deposition occurred irrespective of virus production. On the other hand, the C-3 deposition was not observed on two quail cell lines transformed by a chemical carcinogen, QE cells infected with avian leukosis virus or normal QE cells. Moreover, QE cells infected with a temperature-sensitive mutant of RSV activated the complement at 37 degrees C but not at 41 degrees C. Since the progeny virus was generated even at 41 degrees C, viral molecules on the cell surface may not play an essential role for the activation. The activation of complement was blocked by EDTA but not by EGTA-Mg++. Therefore, the complement activation on the transformed cells appears to be mediated via the alternative complement pathway (ACP). Similar results were obtained with the complement consumption test; the residual cytolytic activity of fresh quail serum via ACP was markedly reduced by pre-incubation of the serum with transformed cells.