Search

The protective immunity conferred by T-cell subsets against infection with Treponema pallidum subsp. pertenue was studied. We demonstrated that hamster T cells can be separated into two subsets by monoclonal antibody (MAb) GK 1.5 (anti-L3T4) and MAb 38. Eighty-five percent of hamster thymocytes were L3T4+ and 87% were 38+ cells; 84% were dual positive for MAbs anti-L3T4 and 38. In the peripheral lymph nodes, however, the L3T4+ and 38+ T cells were mutually exclusive according to two-color immunofluorescence analysis. The two T-cell subsets were found to be functionally distinct according to their secretion of interleukin 2 (IL-2) when stimulated with concanavalin A. The L3T4+ cells secreted IL-2 and had characteristics of T helper cells, while the 38+ cells did not secrete IL-2 and appeared to be T cytotoxic-suppressor cells. Transfer of 4 x 10(6) helper or cytotoxic-suppressor T lymphocytes from T. pallidum subsp. pertenue-immune hamsters protected irradiated naive hamsters against challenge with this subspecies. IL-2 production could still be detected in the irradiated recipients 12 days after irradiation of naive recipients, although at a low level. This suggests that the remaining lymph node cells could support the survival and expansion of the infused cytotoxic-suppressor T cells. No accumulation of macrophages was observed in regional lymph nodes of immune T-cell recipients within 10 days of infection. Instead, there was an influx of polymorphonuclear neutrophils in all animals injected with T. pallidum subsp. pertenue. This report demonstrates that hamster T cells can be separated into two phenotypically and functionally distinct subsets and that both T-cell subsets confer protection against challenge with T. pallidum subsp. pertenue.

Experimental studies have indicated that macrophages are involved in the pathogenesis of syphilis. Whether macrophages alone or with immune serum are ultimately responsible for killing of treponemes is disputed. We have demonstrated that BCG-vaccinated hamsters administered normal serum contained fewer treponemes in the inguinal and popliteal lymph nodes than did the nonvaccinated controls. When BCG-vaccinated hamsters were injected with syphilitic immune serum and challenged with Treponema pallidum ssp. endemicum, treponemicidal activity was enhanced. Treponemicidal activity was also detected in BCG-vaccinated hamsters challenged with treponemes treated in vitro with immune serum and its immunoglobulin fractions, especially IgG2. The immune IgG2 fraction had more treponemicidal activity than did the immune IgG1 fraction and the unfractionated immune serum. Our observations indicate an important synergistic role for macrophages and immune serum, especially IgG2, for elimination of T. pallidum ssp. endemicum from the host.