Co-stimulatory signals increase the reactivity of gamma delta T cells towards mycobacterial antigens

Although it has been shown that gamma delta T lymphocytes are able to react with different cell-associated or soluble antigens, the immune repertoire of these cells appears to be skewed to the recognition of mycobacterial ant igens. We have studied the number and reactivity of gamma delta T cells tow ards several mycobacterial antigens in patients with tuberculosis and lepro sy, as well as their healthy contacts and control individuals. We found an increased number of V delta 2(+) cells in healthy contacts (PPD+ and leprom in(+)) and tuberculoid leprosy patients. The gamma delta T cells from lepro matous leprosy showed a decreased response to all antigens tested, but some of these patients exhibited a significant response to the 30-kD glycoprote in of Mycobacterium tuberculosis. Interestingly, the reactivity of gamma de lta T cells against mycobacterial antigens was significantly increased by c ostimulatory signals generated through CD7, LFA-1, CD50 and CD69 in all gro ups. However, signalling through CD69 did not enhance the responsiveness of gamma delta lymphocytes from lepromatous patients. On the other hand, the in vitro blockade of IL-10 with a specific antibody enhanced the cell proli feration of gamma delta lymphocytes from lepromatous leprosy patients, wher eas exogenous IL-10 had an opposite effect in most individuals studied. The se results suggest the potential role of different cell membrane receptors in the regulation of gamma delta T cell proliferation induced by mycobacter ia, as well as the possible involvement of IL-10 in this phenomenon.