Functional Immaturity of Bone Marrow Bands and Polymorphonuclear Leucocytes

Summary. Neutrophilic granulocytes from peripheral blood and from bone marrow were compared with respect to their ability to ingest paraffin oil droplets coated with bovine serum albumin or E. coli lipopolysaccharide. Granulocytes were incubated with unopsonized droplets or with droplets opsonized with fresh human serum. While myeloblasts and promyelocytes did not ingest either type of droplet, some myelocytes and metamyelocytes engulfed droplets; bands and polymorphonuclear leukocytes were the most active phagocytes. Morphologically mature granulocytes of bone marrow, in contrast to those of peripheral blood, had an ingestion defect for unopsonized droplets that was only partially corrected by heat‐labile opsonin. A dissociation between functional and morphologic maturity can therefore be demonstrated in bone‐marrow granulocytes.