Immune-mediated adherence of eosinophils to Toxocara canis infective larvae: the role of excretory-secretory antigens.

The participation of Toxocara canis larval excretory-secretory antigens in immune-mediated adherence was determined in vitro. Adsorption of immune sera with excretory-secretory antigens removed some complement components, removed IgG antibody directed against larval surfaces, and abrogated all adherence observed with untreated immune serum. At least four antigens could be implicated in adherence, by Western blot analysis of adherence mediating sera. Scanning and transmission electron microscopic examination of larval-eosinophil interactions revealed that eosinophils adhered to a membranous sheath-like layer that was frequently detached from the larval epicuticle. The layers appeared to be composed of surface antigens and antibody, and may provide larvae with protection against antibody and eosinophil toxins by preventing their contact with the epicuticle. The release of surface antigens also may be important in allowing larvae to evade the host's immune response by facilitating the removal of antibody and eosinophils from the larval surface.