Abstract Immunoglobulin and other serum proteins of the pig host were found in Taenia solium cysticercus antigen extracts by immunodiffusion and immuno-electrophoresis. By the immunoenzyme technique using peroxidase coupled to antibody, it was shown with electron microscopy that the microvilli on the surface of the bladder wall bind appreciable amounts of pig serum globulin. Ultrastructural analysis also demonstrated that whole larvae showed large areas in which the microvilli were lost, leaving an intact basement membrane which also has host serum proteins attached to it.