T cells with receptors for IgD

The role of IgD in the immune response has been elusive, although its predominance on the cell surface suggests a receptor function. We have shown previously that euthymic but not athymic BALB/c mice, injected with IgD before antigen, exhibit enhanced antibody responses which can be transferred by T cells 1,2 . Isotype-specific T cells have been reported to have both upward and downward immunoregulatory effects 3–5 . Here we demonstrate the existence of T cells with receptors for IgD, and show that exposure to IgD in vivo or in vitro significantly increases the number of T δ cells in the spleen and lymph nodes but not in the thymus. The kinetics of T δ -cell appearance in vivo parallels that of the immunoenhancing effect which occurs after injection of IgD. These T δ cells are of the Lyt 1 + 2 − T-cell phenotype.