Comparative studies of functional characteristics of mononuclear cell subsets and granulocytes

Two human peripheral blood monocyte subsets and lymphocytes were isolated by counterflow centrifugal elutriation (CCE). The cell volumes of 303 mu3 and 380 mu3 were measured for the smaller and larger monocyte populations, respectively. Superoxide release by large monocytes exposed to opsonized zymosan was five times more active than that of the small monocytes. The production of colony stimulating activity was two-fold greater and the myeloperoxidase activity was 1.4-fold greater by the larger monocytes. Enriched fractions of cytotoxic cells responsible for natural killer (NK) activity against neuroblastoma cells were also obtained by counterflow centrifugal elutriation. Natural killer cells were obtained in larger lymphocyte fractions and had a mean cell volume of 180 mu3. Compared with the NK activity against the neuroblastoma cells, both the small and large monocytes displayed greater antibody-dependent cellular cytotoxicity (ADCC) activity against human erythrocytes. The larger peripheral blood monocytes aggregated in response to FMLP (N-formyl-methionyl-leucyl-phenyl alanine peptide) and PAF (platelet activating factor). Unlike the granulocyte, monocyte aggregation in response to FMLP was not accompanied by degranulation nor was it potentiated by cytochalasin B. In addition, monocyte aggregation could be blocked by benoxaprofen, unlike the granulocyte. Thus, CCE provides a means of isolating subsets of monocytes and lymphocytes and obtaining large numbers of peripheral blood monocytes for functional studies.