Mycobacterial Di-O-acyl-trehalose inhibits mitogen- and antigen-induced proliferation of murine, T cells in vitro

2,3-Di-O-acyl-trehalose (DAT) is a glycolipid located on the outer layer of the Mycobacterium tuberculosis cell envelope. Due to its noncovalent linka ge to the mycobacterial peptidoglycan, DAT could easily interact with host cells located in the focus of infection. The aim of the present work was to study the effects of DAT on the proliferation of murine spleen cells. DAT was purified from reference strains of M. tuberculosis, or M. fortuitum as a surrogate source of the compound, by various chromatography and solvent e xtraction procedures and then chemically identified. Incubation of mouse sp leen cells with DAT inhibited in a dose-dependent manner concanavalin A-sti mulated proliferation of the cells., Experiments, including the propidium i odide exclusion test, showed that these effects were not due to death of th e cells. Tracking of cell division by labeling with 5,6-carboxyfluorescein diacetate succinimidyl ester revealed that DAT reduces the rounds of cell d ivision. Immunofluorescence with an anti-CD3 monoclonal antibody indicated that T lymphocytes were the population affected in our model. Our experimen ts also suggest that the extent of the suppressive activity is strongly dep endent on the structural composition of the acyl moieties in DATs. Finally, the inhibitory effect was also observed on antigen-induced proliferation o f mouse spleen cells specific for Toxoplasma gondii. All of these data sugg est that DAT could have a role in the T-cell hyporesponsiveness observed in chronic tuberculosis.