Ultrastructural and immunophenotypic differentiation of dendritic cells from mouse bone marrow cultures supplemented...

The present study examined electron microscopical, immunohistochemical and morphometric changes in the development, differentiation, and maturation of dendritic cells in the culture of mouse bone marrow cells supplemented with granulocyte/macrophage colony-stimulating factor (GM-CSF). A large number of large dendritic cells were released from the aggregates of small round cells. These released cells showed morphological, immunophenotypic, and functional characteristics of typical dendritic cells. These dendritic cells possessed irregularly-shaped nuclei in abundant cytoplasm with rough endoplasmic reticulum (rER), vesicles, multivesicular bodies, and tubulovesicular system, and projected long dendritic cytoplasmic processes. The tubulovesicular system and dendritic surface projections were characteristic of interdigitating cells usually residing in the paracortical area of lymph nodes. Small cells in aggregates were round in shape, had oval nuclei in narrow cytoplasm with poorly developed intracellular organelles, and projected a few short processes. These cells were a proliferating population distinct from monocytes in both ultrastructure and immunophenotype. Morphometrical analysis of cultured cells provided evidence that the small cells differentiate into typical dendritic cells via intermediate cells. These results imply that dendritic cells differentiate from small round dendritic precursor cells and that GM-CSF is a major cytokine capable of inducing the development, differentiation, and proliferation of dendritic cells.