title: LPS regulation of the immune response: suppression of immune responses to orally administered T-independent antigen.
abstract: The regulation of immune responses to gastrically administered TI antigens has been investigated, and the characterization of a regulatory cell population has been performed. Intragastric administration of TNP-haptenated homologous erythrocytes (TNP-MRBC) induced splenic IgM anti-TNP PFC responses in LPS nonresponsive C3H/HeJ mice that were higher than those in LPS-responsive C3H/HeN mice and similar to those noted in athymic (nu/nu) C3H/HeN animals. The simultaneous intragastric administration of LPS with TNP-MRBC augmented immune responses in a manner similar to that previously reported for parenterally administered LPS and antigen. Further, LPS-induced augmentation of TNP-MRBC responses was greater in athymic mice. These findings were substantiated using in vitro spleen cultures. Intragastric challenge with a 2nd TI antigen, TNP-LPS, induced approximately 8-fold higher splenic anti-TNP PFC responses in athymic C3H/HeN mice compared with those in euthymic littermates. By admixture of B and T cell populations, it was demonstrated that the host responsiveness to TNP-LPS was negatively regulated by suppressor cells. Suppressive activity resided in a Thy 1.2-bearing, irradiation-resistant, nylon wool-nonadherent cell population. These cells could be demonstrated in spleen and Peyer's patches from young or old LPS-responsive C3H/HeN mice, but not in tissues from LPS nonresponsive C3H/HeJ mice. The specificity of the regulator cells was not limited to TNP-LPS responses, since immune responsiveness to another TI antigen, TNP-dextran, was also under the control of this cell population. These studies confirm the TI nature of TNP-MRBC and indicate that immune responses to gastrically administered antigens such as TNP-LPS, TNP-dextran, and possibly TNP-MRBC are negatively regulated by a suppressor T cell population. A role for endogenous LPS in the generation of regulator cells and the effect of these cells on host responses to gut-derived antigens is discussed.
mesh_terms: D000284:Administration, Oral; D000818:Animals; D000917:Antibody Formation; D003911:Dextrans / Q000008:administration & dosage*; D006462:Hemolytic Plaque Technique; D006736:Horses; D008070:Lipopolysaccharides / Q000494:pharmacology*; D051379:Mice; D008809:Mice, Inbred C3H; D008819:Mice, Nude; D009578:Nitrobenzenes / Q000008:administration & dosage*; D012756:Sheep; D013601:T-Lymphocytes / Q000276:immunology; D014301:Trinitrobenzenes / Q000008:administration & dosage*
chemical_list: D003911:Dextrans; D008070:Lipopolysaccharides; D009578:Nitrobenzenes; D014301:Trinitrobenzenes