Immunoglobulins on the surface of thymus-derived cells engaged in the initiation of a humoral immune response.

Preculture treatment of normal spleen cells with antiserum against mouse kappa light chains and complement was found to inhibit in vitro responses of these cells to TNP and erythrocyte (carrier) antigens, primarily by elimination of a thymus-derived helper component required for the response. Spleen populations inactivated in this way could be reconstituted with irradiated, carrier-immune spleen cells or with carrier-educated thymus-derived spleen cells. The ability of helper populations (i.e. irradiated, carrier-immune spleen cells or carrier-educated thymus-derived spleen cells) to enhance the response of normal spleen cells to hapten was eliminated by pretreatment of the helper cells with anti-kappa serum and complement. No significant effect of anti-kappa and complement treatment on precursor cell populations in normal spleen or bone-marrow-derived spleen could be demonstrated. The data are interpreted as evidence for the presence of immunoglobulin components. The function of these molecules is not established but it would be reasonable to assume that they are involved in antigen recognition, on the surface of thymus-derived cells.