Identification of distinctive stromal elements in erythroid and neutrophil granuloid spleen colonies: light and electron microscopic study.

Erythroid and granuloid spleen colonies from 1100 R irradiated mice transfused with 5 X 10(4) syngeneic bone marrow cells, fixed in paraformaldehyde-glutaraldehyde followed by osmium tetroxide, were processed for light and electron microscopy. Light microscopic examination of day 7 erythroid colonies revealed distinctive reticular cells indigenous to the erythroid colony; they were not observed outside the confines of the erythroid colony or in granuloid colonies or within the spleens of control irradiated mice that had not been transfused with bone marrow cells. Examinations of sections stained with a newly developed differential stain for thick sections (1 mu) revealed unique staining properties for these reticular cells. Ultrastructural features and the intimate contact of the proerythroblasts and the reticular cells are described. Microscopic examination of day 10 neutrophil granuloid spleen colonies harvested from polycythemic mice showed distinctive stromal cells, different from those of erythroid colonies. These distinctive cell to cell relationships constitute a possible morphological basis for the function of the erythroid and granuloid hemopoietic inductive microenvironments.