Population studies showing cross-reactivity of Toxoplasma gondii antibodies with antibodies to malignant cervical tissue antigens.

Antibody inhibition studies have established that ethanol-soluble extracts prepared from a pool of malignant cervical tissues contained substances capable of reacting with antibodies specific for Toxoplasma gondii and malignant tissue factors. Extracts from normal cervical tissue did not possess Toxoplasma or malignant tissue antigens. Antibodies to malignant cervical tissue extract could be detected singly or in combination with Toxoplasma antibodies. The overall incidence of antibodies to malignant tissue extract in over 2,000 samples of blood tested was 4.4%. Of 98 apparently healthy donors with antibodies to malignant tissue extract, 50% also possessed Toxoplasma antibodies. The combined incidence of anti-Toxoplasma activity was 16.5% of all samples tested. Methods for the isolation and determination of IgG antibodies to malignant tissue and Toxoplasma antigen extracts are described, and the possible significance of the findings discussed.