ANTI-I AGGLUTININS IN NON-HUMAN SERA

Summary. Macroglobulin cold haemagglutinins, mostly of anti‐I specificity, were found in high incidence and titre in sera from sheep, cattle, kangaroos, wallabies, wombats and possums living in a range of environments in Australia. There was neither positive nor negative correlation between the I‐antigen content of the cells of the different species and the incidence of cold haemagglutinins. For example, the red cells of laboratory rabbits were still capable of binding radioactively labelled I‐antibody at 37°C, yet the rabbit sera had the weakest cold haemagglutinins in the lowest incidence. It is suggested that these results pointed to a widespread heteroantigen as the aetiological agent involved in the production of anti‐I cold haemagglutinins in animals and man. The configuration of the I‐antigen rather than that of the I‐antibody is probably altered by cooling so that it more closely resembles the heteroantigen. Thus anti‐I cold haemagglutinins would not be true autoantibodies since I does not exist at physiological temperatures in most species. The occurrence in sheep and cattle sera of higher titres of cold haemagglutinins after reinfection with Ostertagia and Trichostrongylus suggests that further studies should be carried out on the possible role of metazoan parasites as aetiological agents in the production of cold haemagglutinins. © 1969 Blackwell Publishing Ltd