Antigen presentation by hapten-specific B lymphocytes. I. Role of surface immunoglobulin receptors

The present study examines the ability of hapten-specific murine splenic B lymphocytes to present hapten-proteins to carrier-specific T cell hybridomas. BALB/cB cells specific for 2,4,6-trinitrophenyl (TNP) were isolated from spleens of immune mice by elution from TNP-gelatin- coated dishes. Such cells presented the TNP-modified terpolymer, GL phi, at concentrations as low as 0.1 microgram/ml, to a GL phi- specific, I-Ed-restricted, interleukin 2-producing T cell hybridoma. In contrast, the same B lymphocytes required 1,000-fold higher concentrations of unmodified GL phi to stimulate the same T cell hybridoma. The presentation of low concentrations of TNP-GL phi by TNP- specific B lymphocytes was significantly or completely blocked by anti- Ig antibody or TNP-proteins, indicating that surface Ig receptors were critically involved in this phenomenon. Finally, binding of TNP- proteins did not alter the ability of the B cells to present unrelated, unhaptenated proteins or to stimulate alloreactive T cells. These results suggest that surface Ig receptors serve to focus antigens onto specific B lymphocytes and that such cells are highly efficient at presenting linked antigenic determinants to T cells. The implications of these findings for the mechanisms of physiologic, histocompatibility- restricted T-B collaboration are discussed.