Splenic T-lymphocyte functions during early syphilitic infection are complex.
Immune regulation during syphilitic infection is extremely complex. This paper presents findings on the early events of T-cell activation following testicular infection in rabbits. Treponema pallidum was preincubated for 24 h with nonadherent spleen cells. After being washed to remove the organisms, these spleen cells were either stimulated with concanavalin A (ConA) to induce interleukin-2 (IL-2), or added to adherent cells that were then stimulated with lipopolysaccharide to induce IL-1. Preincubation with the treponemes up-regulated nonadherent cell functions. These sensitized cells increased their IL-2 production and augmented macrophage IL-1 synthesis. In sharp contrast, if this preincubation step was omitted, down-regulation was apparent. When T. pallidum was directly incubated with nonadherent cells in the presence of ConA, reduced levels of IL-2 were detected. Nonadherent cells from infected rabbits secreted soluble suppressive factors after 48 h of in vitro incubation; these factors inhibited ConA-induced IL-2 generation as well as ConA-induced lymphocyte proliferation. At least some of this suppressive activity was attributed to transforming growth factor. In addition, when T lymphocytes were depleted, less suppression was detected. Treponemes also inhibited ConA-induced T-cell proliferation, and monophosphoryl lipid A reversed this inhibitory effect. Since monophosphoryl lipid A neutralizes T-suppressor activity, these findings further suggest a role for T-suppressor activity during syphilitic infection. Finally, T. pallidum directly stimulated IL-2 synthesis when coincubated with phorbol myristate acetate. This agent reverses the prostaglandin E2 blockage of T-helper cell protein kinase C, a necessary second messenger signal for IL-2 synthesis. In summary, T-cell functions are extremely complex and represent a composite of both stimulation and down-regulation, which occur concurrently but to different degrees.
Department of Medical Microbiology and Immunology, School of Medicine, University of Minnesota, Duluth 55812.
T J
TJ
Fitzgerald
M A
MA
Tomai
D000818:Animals; D003208:Concanavalin A; D007213:Indomethacin / Q000494:pharmacology; D007376:Interleukin-2 / Q000096:biosynthesis*; D008050:Lipid A / Q000031:analogs & derivatives / Q000276:immunology; D008213:Lymphocyte Activation; D011817:Rabbits; D013154:Spleen / Q000276:immunology; D013587:Syphilis / Q000276:immunology*; D013601:T-Lymphocytes / Q000276:immunology*; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D013997:Time Factors; D015291:Transforming Growth Factors / Q000502:physiology; D014210:Treponema pallidum / Q000276:immunology*
D007376:Interleukin-2; D008050:Lipid A; D003208:Concanavalin A; D015291:Transforming Growth Factors; C048436:monophosphoryl lipid A; D013755:Tetradecanoylphorbol Acetate; D007213:Indomethacin