PROTECTION AGAINST ASCENDING INFECTION OF THE GENITAL-TRACT BY CHLAMYDIA-TRACHOMATIS IS ASSOCIATED WITH RECRUITMENT OF MAJOR HISTOCOMPATIBILITY COMPLEX CLASS-II ANTIGEN-PRESENTING CELLS INTO UTERINE TISSUE

A mouse model of ascending infection following intravaginal inoculatio n with a strain of Chlamydia trachomatis isolated from humans has been used to identify immune mechanisms associated with protection against genital infection. BALB/c and C3H mice differed in their susceptibili ties to infection and inflammatory disease. In both mouse strains, asc ension of the organism and recruitment of bone marrow-derived mononucl ear leukocytes were evident in uterine tissue 1 week postinfection, By 3 weeks the organism had been cleared and inflammation had been resol ved in the BALB/c mice, but both persisted in the C3H animals. In athy mic nude BALB/c mice both the organism and inflammation persisted, ind icating the influence of the hosts' immune response on the outcome of infection. Both BALB/c and C3H mice had a Th1 response in draining lym ph nodes, with predominant production of gamma interferon and tumor ne crosis factor alpha, low levels of interleukin-10, and no detectable l evels of interleukin-4. However, the composition of the early uterine infiltrate differed in these two mouse strains. Cell surface labeling and analysis of light scatter properties by flow cytometry identified a population of large, CD45(+) major histocompatibility complex class II mononuclear cells, which were a prominent feature of the infiltrate s in BALB/c mice but were present in significantly lower numbers in C3 H mice, These cells expressed the costimulatory molecules CD86 and CD4 0 and stimulated allogeneic T cells, suggesting that these mononuclear cells are a population of antigen-presenting cells and that they may play a role in clearing antigen and protecting against inflammatory di sease in BALB/c mice. An additional level of immunological control may thus exist in genital chlamydial infection.