Dendritic cells of the mouse: Identification and characterization

We have identified and characterized a distinctive population of dendritic cells (DCs) in mouse spleen, lymph nodes, thymus, and liver. Dendritic cells can adhere to tissue culture surfaces but otherwise differ considerably from macrophages, the other major class of adherent cell. Morphological differences are evident by phase contrast and electron microscopy, and by cytochemistry. Dendritic cells exhibit little or no binding and phagocytosis of opsonized particles. During culture, they retain their unusual morphological features and surface markers, but lose the capacity to adhere. All DCs express and synthesize Ia antigens for several days in vitro, whereas only a subpopulation of mouse macrophages expresses Ia in all organs we have studied. Thus, DCs can be distinguished from macrophages in several independent and stable traits. Highly enriched preparations of the 2 cell types have been obtained. Spleen DCs are derived from bone marrow and are present in nude mice. Dendritic cells do not proliferate, but exhibit a rapid turnover. Other features in their life history are not known. We are studying the contribution of DCs to several immune responses. In all organs we have studied, they are powerful stimulators of the primary mixed leukocyte reaction. B cells, T cells, and macrophages from these organs are weak or inactive. Dendritic cells are potent accessory cells in T cell proliferative responses to mitogens and tuberculin antigens. These dendritic cells and Langerhans cells may belong to a similar lineage, but to date, Birbeck granules, surface ATPase, and binding of opsonized erythrocytes have not been demonstrated in spleen dendritic cells. However, in functional assays, both DCs and Langerhans cells synthesize Ia antigens and contribute to transplantation reactions, accessory cell function, and the development of contact sensitivity