Deficient Humoral Responses Underlie Susceptibility to Toxoplasma gondii in CD4-Deficient Mice
AUTOR(ES)
Johnson, Lawrence L.
FONTE
American Society for Microbiology
RESUMO
Resistance to infection with Toxoplasma gondii was studied in mice lacking CD4 expression. Such mice developed more brain cysts and survived for a shorter time than did wild-type controls after peroral infection with ME49 cysts. After immunization with the ts-4 strain of T. gondii, CD4-deficient mice exhibited impaired resistance to a challenge infection with virulent RH tachyzoites. Thus, deficient CD4 expression increases the susceptibility of mice to a primary peroral T. gondii infection with cysts and impairs their ability to be successfully vaccinated. CD8+ T cells from blood or spleens of Toxoplasma-infected, CD4-deficient mice expressed markers of activation at frequencies similar to those of infected wild-type mice. Production of IFN-γ in vitro was moderately depressed, and levels of Toxoplasma-specific immunoglobulin G2a in serum were substantially lower than in wild-type mice. Administration of Toxoplasma-immune serum to ts-4-vaccinated CD4-deficient mice significantly improved their resistance to RH challenge. Also, the survival of CD4-deficient mice chronically infected with ME49 was significantly prolonged by administration of immune serum. These results demonstrate that in addition to CD8+ T cells and IFN-γ, which are known to be critical for resistance, CD4+ cells also contribute significantly to protection against chronic T. gondii infections and against challenge infections with highly virulent tachyzoites in immunized mice via their role as helper cells for production of isotype-switched antibodies.
ACESSO AO ARTIGO
http://www.pubmedcentral.nih.gov/articlerender.fcgi?artid=127596Documentos Relacionados
- Virus-specific CD8+ T cell numbers are maintained during γ-herpesvirus reactivation in CD4-deficient mice
- CD4-mediated and CD8-mediated cytotoxic and proliferative immune responses to Toxoplasma gondii in seropositive humans.
- Interleukin-15-Deficient Mice Develop Protective Immunity to Toxoplasma gondii
- Depletion of L3T4+ (CD4+) T lymphocytes prevents development of resistance to Toxoplasma gondii in mice.
- Susceptibility of Interleukin-2-Deficient Mice to Toxoplasma gondii Is Associated with a Defect in the Production of Gamma Interferon