Lymphoid dendritic cells are potent stimulators of the primary mixed leukocyte reaction in mice.

Abstract

Dendritic cells (DC) are a new cell type initially identified in mouse lymphoid organs. Recently, DC were purified from mouse spleen. This paper demonstrates a functional role of DC: they are potent stimulators of the primary mixed leukocyte reaction (MLR). As few as 300-1000 DC doubled the proliferative activity of 5 .times. 106 allogeneic responder spleen cells, while 0.3-1.0 .times. 105 DC induced a maximal stimulation of 30- to 80-fold. Between these extremes, the log of the MLR response increased linearly with the log of DC numbers. This dose-response assay was then used to compare the potency of purified DCs with that of other heterogeneous lymphoid populations, many of which gave dose-response curves with similar slopes. The potency of purified DC as MLR stimulators was 100-200 times greater than that of unfractionated spleen cells. When spleen cells were fractionated by simple physical techniques, MLR-stimulating capacity in the subpopulations correlated closely with DC numbers. Removal of splenic B [bone marrow derived] or T [thymus derived] lymphocytes by anti-immunoglobulin or anti-brain serum plus complement did not reduce MLR-stimulating capacity. Several populations enriched in mononuclear phagocytes but lacking in DC stimulated weakly if at all. DC are a potent stimulating cell and are at least 100 times more effective than other major cell subclasses, i.e., B and T lymphocytes and macrophages.