The role of gamma delta T cells in immunoregulation is largely unknown. In
the current study we noted that gamma delta T cells play a positive role in
the humoral response. These positively acting gamma delta T cells are requ
ired for the successful adoptive cell transfer of the humoral response, as
well as for in vitro generation of plaque-forming cells (PFC). The presente
d results show that gamma delta T cells cause an increase in interleukin-10
(IL-IO) production, which partly elucidates the mechanism of action of the
se cells. However, experiments with cell culture inserts strongly suggest t
hat direct cell-cell contact between immune and gamma delta H-2-compatible
regulatory T cells is critical to the exertion of the positive immunoregula
tory function of gamma delta cells. The mechanism of cross-talk between the
se two cell populations is still not clear but we regard as most likely tha
t the positively acting gamma delta T cells may interact with a complex of
heat-shock protein-non-polymorphic MHC (IB) on the surface of T helper type
2 and/or B cells. This could provide, by direct cell-cell contact, the cog
nate recognition between gamma delta T-cell receptors and heat-shock protei
n-MHC that leads to positive internal signalling in the immune cells.