title: In vivo effects of monoclonal anti-L3T4 antibody on immune responsiveness of mice infected with Schistosoma mansoni. Reduction of irradiated cercariae-induced resistance.
abstract: Mice can be partially protected against challenge infections of Schistosoma mansoni cercariae by either single or multiple exposure to irradiated cercariae (x-cerc). The participation of L3T4+ lymphocytes on this resistance phenomenon was evaluated by selectively depleting this cell population through in vivo administration of mAb anti-L3T4 (hybridoma GK 1.5) at three different times in relationship to the challenge infections. Treatment with anti-L3T4 before challenge such that depletion was effective during the time of cercarial skin penetration and dermal/s.c. residence significantly reduced the level of resistance induced by x-cerc sensitization. When treatment was delayed until after challenge, depletion of L3T4+ cells coincided with either the lung or post-lung/liver phases of schistosomular migration, and normal levels of x-cerc-induced resistance were induced. In contrast to once-immunized mice, mice hyperimmunized by five exposures to x-cerc and then depleted of L3T4+ cells at the time of challenge (skin phase) still expressed resistance to the challenge. These data suggest that when mice are sensitized only once with x-cerc the challenge infection provides a necessary immunologic boost which requires L3T4+ cells for effective expression of resistance. The requirement for this anamnestic effect by the challenge infection can be circumvented by hyperimmunization. Evaluation of the immune response of one-time sensitized or hyperimmunized mice demonstrated that cellular Ag-specific proliferative responses and mitogen-induced lymphokine production were abrogated after any of the various in vivo regimens of anti-L3T4 antibody. In contrast, immunoblot analysis of humoral responsiveness revealed a correlation between the expression of resistance and the ability of sera from immunized and anti-L3T4 treated mice to recognize a 75-kDa parasite antigenic component.
mesh_terms: D000818:Animals; D000909:Antibodies, Helminth / Q000096:biosynthesis; D000911:Antibodies, Monoclonal / Q000008:administration & dosage / Q000276:immunology*; D000945:Antigens, Differentiation, T-Lymphocyte / Q000276:immunology*; D006790:Host-Parasite Interactions; D007113:Immunity, Innate; D007814:Larva / Q000528:radiation effects; D008198:Lymph Nodes / Q000473:pathology; D008212:Lymphocyte Depletion; D051379:Mice; D012550:Schistosoma mansoni / Q000254:growth & development / Q000276:immunology; D012555:Schistosomiasis mansoni / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D014611:Vaccination
chemical_list: D000909:Antibodies, Helminth; D000911:Antibodies, Monoclonal; D000945:Antigens, Differentiation, T-Lymphocyte