Thymus immunoglobulin receptors. Ontogenic development, response to antigenic stimulation and their possible role in the regulation of "aggressive" immune reactions.

IgG, IgA and IgM receptors were detected on mouse thymocytes with a cytotoxic assay. IgG receptors were only detectable during the postnatal period, while the IgA and IgM were also present on thymocytes from adults. IgA cells were more abundant in neonates. Thymus receptors of the three classes were immunochemically unrelated to spleen receptors. IgA and IgM thymus cells responded to antigenic stimulation with SRBC by proliferation and exposure of new, class-specific antigenic determinants, whereas spleen cells did not. The possible role of thymus receptors may be regulatory by inhibition of the humoral and cellular `aggressive' immune reactions.