The Role of Mononuclear Phagocytes as Accessory Cells in Lymphocyte Responses

For some time it has been known that certain immunologic functions of lymphocytes require the addition of mononuclear phagocytes in order to be operative. Historically, Mosier and Coppleson (1968) initially described a need for adherent cells in animal in vitro primary immune responses. As the supportive role of adherent cells in immune responses became apparent, efforts were made to identify the lineage of this accessory cell. The evidence to date indicates that although a number of cells can function as accessory cells, mononuclear phagocytes are the predominant accessory cell type operational in many current immunologic assay systems. Mononuclear phagocytes have been employed as accessory cells in both their blood monocyte and tissue macrophage forms; both animal and human research systems abound.