The production of human A and B blood group like substances by in vitro maintained second stage Toxocara canis larvae: their presence on the outer larval surfaces and in their excretions/secretions.

In vitro maintained second stage Toxocara canis larvae do not bind polyclonal anti-human A or B blood group antibodies onto their outer surface at 37 degrees C as detected by indirect fluorescence. When larvae are incubated at 2 degrees C under the same experimental conditions, intense fluorescence over the whole outer surface is observed. Re-incubation of such larvae at 37 degrees C results in a gradual loss of surface fluorescence. This loss is complete after 3 h. The excretions/secretions (ES) of in vitro maintained larvae can neutralize the reactivity of polyclonal anti-human A and B typing antisera against their respective erythrocytic antigens. Rabbits infected with T. canis infective eggs or immunized with ES produce elevated isohaemagglutinin titres against A and B erythrocyte antigens. The presence of epitopes, on the outer surfaces of T. canis larvae and in ES, which cross-react with human ABO blood group antibodies must be borne in mind when larvae or their products are used for the serodiagnosis of human toxocaral larva migrans.