Heterologous reactions involving parasites, blood group antibodies and tissue components.

The sera of many patients with malaria and filariasis, and also anti-A and B blood group sera, were found to react by immunofluorescence with the somatic musculature of nematodes, especially Ascaris, and human and rat muscle, especially the skeletal type. These reactions were attributed to a polysaccharide related to AB substance in adult nematodes and to raised AB antibodies in malaria. Similar heterologous reactions were found to involve the integument of schistosome adult worms and the microfilariae of Loa loa, which were attributed to the incorporation of host AB blood group substances into the parasite. Other parasites and sera gave mainly negative results. These heterologous reactions constitute a potential hazard in immunofluorescence tests, against which skeletal muscle provides a control. The antibodies concerned were not operative in complement fixation tests, but there was a relationship to anti-complementary activity which suggested the transient presence of a circulating antigen.