To study antigen-specific immune responses of gut-associated T lymphocytes after gastrointestinal infection, Cynomolgus monkeys were inoculated rectally with Chlamydia trachomatis of the L2 [lymphogranuloma venereum (LGV)] strain. Infected monkeys developed a chronic proctitis with the appearance of LGV-specific immunoglobulin G-antibodies in the serum. Lymphocytes isolated from the peripheral blood, the spleen, and draining lymph nodes had a vigorous antigen-specific proliferative response to LGV in vitro. Both T and B cells proliferated in response to stimulation with LGV, but B-cell proliferation was T-cell-dependent, as shown by cell separation techniques and cell-cycle analysis with dual-laser flow cytometry. Lymphocytes isolated from both involved and uninvolved lamina propria did not proliferate in response to LGV stimulation, whereas mitogen-induced proliferation was not different in lamina propria lymphocytes and the other lymphocyte populations. This lack of antigen-specific proliferation was not caused by a suppressor effect of mucosal T cells or monocytes or the absence of antigen-presenting cells. In contrast, lamina propria T lymphocytes from infected animals were able to provide antigen-specific help for polyclonal immunoglobulin synthesis by immune B lymphocytes after stimulation with LGV. Thus, in LGV proctitis in monkeys, mucosal antigen-reactive T cells differ from lymphocytes in other sites in that they can provide helper function, but are not able to proliferate in response to LGV antigens.
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