Heterogeneity of stimulator cells in the murine mixed leukocyte response

Abstract

Mouse spleen cells were fractionated and tested for their ability to stimulate a primary mixed leukocyte response (MLR). Several nonlymphoid populations were stimulatory, purified dendritic cells and 18‐h adherent macrophages being the most effective. B and T lymphocytes and peritoneal washout cells were almost ineffective by comparison. This hierarchy of stimulator potential was observed whether the genetic difference between stimulator and responder was whole H‐2 or H‐2 subregion (K. D. I. I‐J). Allostimulatory populations contained a high proportion of cells expressing I region determinants. The functional importance of these antigens was confirmed using specific anti‐I region antisera. Thus, it appears that stimulator cells in the MLR are heterogeneous, Ia‐bearing, and of “accessory” rather than lymphoid type.