Search

The role of Ia antigens expressed at the level of the antigen-presenting cell (APC) or macrophage has been firmly established as essential to the process of antigen recognition by T cells (1, 2). The observation that only responder but not nonresponder parental macrophages can present the relevant immune response (Ir) gene controlled antigen to (responder x nonresponder)F1 T lymphocytes suggested that the Ir gene products are functionally expressed at the level of the APC (3). Further studies on the Ir gene control of T cell responses to native and synthetic insulin polypeptides (4, 5) were consistent with the view that the ability to select and display a specific antigen epitope to the immune T cell is an Ir gene function expressed by the APC-the “determinant selection model.”