title: Gene knockout mice establish a primary protective role for major histocompatibility complex class II-restricted responses in Chlamydia trachomatis genital tract infection.
abstract: Mice with disrupted beta 2-microglobulin (beta 2m-/-), I-A (class II-/-), or CD4 (CD4-/-) genes were examined for their capacity to resolve Chlamydia trachomatis genital tract infection. C57BL/6 and beta 2m-/- mice resolved infection similarly and were culture negative by 4 to 5 weeks following infection. Conversely, major histocompatibility complex (MHC) class II-/- mice failed to resolve infection, and CD4-/- mice showed a significant delay (2 weeks). Secondary challenge of C57BL/6, beta 2m-/-, and CD4-/- mice established that acquired protective immunity, which was characterized by an infection of shortened duration and reduced shedding of infectious organisms, developed. Serological analysis of C57BL/6 and beta 2m-/- mice by enzyme-linked immunosorbent assays revealed no striking differences in the immunoglobulin subclass specificity of the anti-Chlamydia response, although some differences were observed in the magnitude of the immunoglobulin G2a (IgG2a) and IgG2b responses. Class II-/- mice produced lower-titered serum anti-Chlamydia antibodies of all isotypes. The serum antibody responses of CD4-/- mice were similar to those of C57BL/6 mice, except that the anti-Chlamydia IgA response was delayed by approximately 3 weeks. Analysis of vaginal washes for Chlamydia-reactive antibodies revealed the presence of IgG2a, IgG2b, and IgA in C57BL/6 and beta 2m-/- mice and primarily of IgA in CD4-/- mice. Vaginal washes from class II-/- mice were consistently antibody negative. Interestingly, the Chlamydia-specific IgA response in the vaginal washes of CD4-/- mice was delayed, but its appearance coincided with decreased shedding of infectious organisms and resolution of infection. Our results demonstrate that MHC class II-restricted T-cell responses are necessary for the development of protective immunity to Chlamydia genital tract infection and that local (vaginal) anti-Chlamydia IgA antibody coincides with the resolution of infection. A substantive role for MHC class I-restricted T-cell responses in protective immunity to Chlamydia genital tract infection was not confirmed.
authors.affiliation: Laboratory of Intracellular Parasites, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Hamilton, Montana 59840, USA.
authors.forename: R P
authors.initials: RP
authors.lastname: Morrison
authors.forename: K
authors.initials: K
authors.lastname: Feilzer
authors.forename: D B
authors.initials: DB
authors.lastname: Tumas
mesh_terms: D000818:Animals; D000907:Antibodies, Bacterial / Q000097:blood; D015704:CD4 Antigens / Q000235:genetics / Q000276:immunology; D002690:Chlamydia Infections / Q000276:immunology* / Q000473:pathology; D002692:Chlamydia trachomatis / Q000276:immunology*; D005260:Female; D005831:Genital Diseases, Female / Q000276:immunology* / Q000473:pathology; D006367:HeLa Cells; D000949:Histocompatibility Antigens Class II / Q000276:immunology*; D006801:Humans; D006968:Hypersensitivity, Delayed; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D013601:T-Lymphocytes / Q000276:immunology; D001613:beta 2-Microglobulin / Q000172:deficiency / Q000235:genetics / Q000276:immunology
chemical_list: D000907:Antibodies, Bacterial; D015704:CD4 Antigens; D000949:Histocompatibility Antigens Class II; D001613:beta 2-Microglobulin