Association of alkaline-phosphatase-positive reticulum cells in bone marrow with granulocytic precursors.

Abstract

In the bone marrow, an elaborate stroma forms the structural basis of the hemopoietic microenvironment. In this study, 2 different types of stromal cells were identified with certainty on tissue sections of intact bone marrow of rats and mice using light microscopic and EM histochemistry. A fibroblast-type reticulum cell was characterized by having alkaline phosphatase associated with its plasma membrane, the alkalinephosphatase-positive reticulum cell (Al-RC). It was closely associated with granulocytic precursors, particularly myeloblasts and neutrophilic promyelocytes. These reticulum cells could be found throughout the marrow but were concentrated near the endosteum. A macrophage-type of reticulum cell was characterized by abundance of lysosomal acid phosphatase and was mainly associated with erythroid precursors (as observed by others). In contrast to the above-mentioned cell type, this latter cell was distributed uniformly throughout the marrow. The Al-RC were apparently mesenchymal stromal cells necessary for granulocytic differentiation in bone marrow.