Excretory-secretory products of Toxocara canis larvae have been considered as a major functional antigen in immune responses against toxocariasis. We studied ultrastructural localization of T. canis second-stage larval antigen using a seropositive human serum under immunogold electron microscopy. High-density gold particles were observed in the secretory cells, excretory duct, intestinal epithelium, and cuticle of the larval worm sections. The distribution of the positive reactions in the larval worms suggests that the nature of the antigen is excretory-secretory antigen including waste metabolites and secretory enzymes.
Animals ; Antigens, Helminth/*immunology/ultrastructure ; Humans ; Larva/*immunology/ultrastructure ; Toxocara canis/*immunology/ultrastructure ; Toxocariasis/*immunology

The author reported previously on separation of the outer tegument of the spargana (plerocercoids of Spirometra mansoni) using high concentration of urea solution. To determine which layer of the tegument is separated by this method, an electron microscopic analysis has been processed in this study. It was confirmed that the basement layer of the tegument is separated from the parenchyme of the sparganum. In addition, the antigenicity of the separated outer tegument against the human sparganosis patient sera was evaluated. Numerous antigenic proteins, including 16 and 55 kDa proteins, were noticed in the separated tegument; however, there were no diagnostic 31/36 kDa molecules in this tegument. The molecules reactive with the patient sera in the tegument are to be characterized in future studies.
Animal Structures/immunology/ultrastructure ; Animals ; Antigens, Helminth/chemistry/*immunology/isolation & purification ; Helminth Proteins/chemistry/*immunology/isolation & purification ; Humans ; Immunoblotting ; Mice ; Mice, Inbred BALB C ; Microscopy, Electron ; Molecular Weight ; Sparganum/*immunology/*ultrastructure