We reported new monoclonal antibodies (moAb), MBS1-3, that raised against long term cultured mouse bone marrow stromal cells (MBSC). They were obtained from a hybridoma prepared by fusion of NS-1 mouse myeloma cells with splenic cells of rat immunized with MBSC. MoAb MBS1 (Ig G2a) recognized the cellsurface determinant mMBS1 (M.W. 10kD) on so-called blanket cells in MBSC. Immunohistochemical analysis showed that moAb MBS1 reacted with dendritic cells in red pulp cord and marginal inner zone of spleen and in perisinusoidal space of liver. We examined bone marrow, spleen and liver which were obtained from syngenic bone marrow transplanted mice (BMT mouse) after lethal irradiation and phenylhydrazine induced hemolytic anemia mice. Dendritic cells which beared MBS1 distributed in the erythroid developing colony in red pulp of spleen, bone marrow and liver of BMT mice and anemic mice. It was suggested that the dendritic cells were highly concerned with erythrocytes proliferation. We also examined the MBSC under some kinds of cytokines stimulation. The number of moAb MBS1 positive cells were increased under IL-1, IL-3 or GM-CSF stimulation. Other two moAbs, moAb MBS2 (Ig G1) reacted with fibrobalstic reticulum cells, moAb MBS3 (Ig G1) reacted with endoth-elial cells and macrophages in MBSC. Stromal cells which beared these two moAbs were little related with hematopoiesis by the examination of BMT or anemic mice.
