[Interaction of the parasitic antigen cytolipin P with erythrocyte factor P1].

Glycolipid compounds causing agglutination of erythrocytes in vitro and the appearance of the anti-P-antibodies in vivo have been named P antigens. The P denotes blood group factor P, being the antigen belonging to multiple allelomorphs in the P system. Their structure has been shown to be of glycosphingolipid nature differing in number and character from carbohydrate components. It has been established that at infestations by parasites the titre of the anti-P-antibodies increases, and hydatid fluid from the cysts of Echinococcus granulosus, as well as certain tissue extracts of some helminths inhibit agglutination of the P1-erythrocytes by anti-P1--antisera. We have isolated the very polar glycolipid complex from hydatid fluid of the cysts of Echinococcus granulosus and from the tissue homogenates of some parasite helminths. We have named it as cytolipin P, designating by P its parasitic origin. The complex is immunologically active and induces cellular and humoral immune response. Having taken into account the nature of cytolipin P we investigated its biological relation to blood group P-factor. Equine, sheep and human p1-erythrocytes agglutinate the cytolipin P when the concentration of it reaches 75--100 mg%. The inhibition of agglutination was achieved by four sequential doses inducing haemagglutination with anti-P-sera when used as standards, and with human anti-P1-sera of the patients exhibiting echinococcal and ascardial positive human and animal sera. Inhibition was reached two times quicker with anticytolipin-P-sera. It would appear that in the organisms invaded by parasites the cytolipin P represents that antigenic structure which provokes the organism to produce the polyclonal anti-P-antibodies.