Interaction between gamma delta T cells and B cells regulating IgG production.

Despite profound knowledge about the molecular structure of the gamma delta T-cell receptor (TCR), the physiological function of gamma delta T cells remains enigmatic. Participation of these cells in complex immune reactions, however, is suggested by the appearance of gamma delta T cells in sites of infectious and autoimmune-induced inflammations. Only a few in vitro models of gamma delta T-cell stimulation have been established: besides a reactivity in the presence of microbial ligands, human gamma delta T cells proliferate upon in vitro challenge with cells from an allogeneic B-lymphoblastic cell line (B-LCL). We present data here demonstrating that this reactivity is not confined to allogenic B-LCL. Autologous B-LCL are also very strong stimulators for gamma delta T cells; more important, autologous B cells can stimulate gamma delta T cells after a period of mitogen-activation but not in a resting state. This activation seems to address a subgroup of gamma delta T cells, as the percentage of V delta 1+ cells is increased after stimulation. Activated gamma delta T cells, on the other hand, are able to exert an influence on B cells by inhibiting the secretion of IgG in coculture experiments. These data define a simple regulatory circle of B cells and gamma delta T cells in vitro and propose a model for gamma delta T-cell function which could explain many in vivo observations of gamma delta T-cell activation.