Anti-phosphoinositide auto-antibodies in sera of cancer patients: isotypic and immunochemical characterization.

High levels of circulating anti-phosphatidylinositol (PtdIns) auto-antibodies (auto-Ab) have been previously found in sera of patients with malignant tumors. Using our ELISA test, a high statistical level of immunological binding directed against PtdIns was found in a large series of sera from patients with proliferative pathologies. In contrast to tumor markers, anti-PtdIns auto-Ab did not vary whatever the histological grades, TMN classification and patient's age. These anti-PtdIns auto-Ab were immunoglobulins (Ig) of G class. Their specificity was evaluated by competition experiments in ELISA and found to be rather high. An increase of these circulating auto-Ab reflected possible disturbances in PtdIns turnover and appearance of endogenous neo-antigen with PtdIns structure.