Antibody response against tetanus toxoid is enhanced by lipopolysaccharide or tumor necrosis factor-alpha in vitamin A-sufficient and deficient rats

Reduced antibody response to tetanus toxoid (TT) was previously demonstrated during vitamin A deficiency but the response to bacterial lipopolysaccharide (LPS) was normal. We addressed whether anti-TT IgG responses are enhanced in vitamin A-sufficient and deficient rats by immunization with LPS plus TT. Antibody responses in vitamin A-sufficient and deficient rats increased significantly after coimmunization (LPS + TT) compared with the response of rats immunized with TT alone. In additional studies, recombinant tumor necrosis factor-alpha (TNF-α) also significantly increased the anti-TT IgG concentrations. Because pretreatment with anti-TNF before coimmunization or immunization with TT alone markedly reduced the anti-TT IgG responses, we infer TNF to be a mediator of both the adjuvanticity of LPS and the unstimulated response to TT. In conclusion, vitamin A-deficient rats can be stimulated to respond to TT by coimmunization with LPS or by treatment with TNF.