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 Tδ cells in the spleen and lymph nodes but not in the thymus. The kinetics of Tδ-cell appearance in vivo parallels that of the immunoenhancing effect which occurs after injection of IgD. These Tδ cells are of the Lyt 1⁺2 ^- T-cell phenotype.