Ia antigen-bearing B cell tumor lines can present protein antigen and alloantigen in a major histocompatibility complex-restricted fashion to antigen-reactive T cells.

Abstract

Several Ia-positive BALB/c B cell tumor lines were screened for their ability to present alloantigen and protein antigens to alloreactive and antigen-reactive T cells. Of 6 Ia-positive tumor lines studied, 3 were effective as antigen presenting cells (APC). On a per cell basis, 1 of the stimulatory lines, A20.3, was substantially more effective than whole spleen cells. The other 3 lines, although Ia-positive, were nonstimulatory. A20.3 was chosen for further study. This tumor appeared to behave like the conventional APC because the tumor cells presented alloantigen, they presented protein in a major histocompatibility complex(MHC)-restricted fashion to both primed donor T cells and to long-term continuous T cell lines, alloantigen presentation was blocked by the inclusion of an anti-Ia antibody in the culture system and A20.3 cells could be effectively pulsed with antigen, although the continuous presence of antigen in the culture system resulted in a superior response. The addition of an exogenous source of interleukin 1 was necessary to obtain an alloreactive but not an antigen-specific T cell response, although inclusion did enhance the magnitude of antigen-stimulated proliferation. These tumor cells should prove useful in studying the biochemical events that occur during antigen processing and the requirements for T cell triggering by processed antigen in association with Ia molecules.