Metabolic and Functional Studies of Monocytes in Congenital Neutropenia

Summary. Children with the severe form of congenital neutropenia usually die from infection by 2 yr of age. Metabolic and functional studies of monocytes from three patients with this disease were undertaken to understand further the role of monocytes in the host's defences against bacterial infection. The bactericidal capacity of monocytes compared favourably to the bactericidal capacity of control neutrophils (PMN). Metabolic studies of monocytes and control leucocytes showed similar stimulation of oxygen consumption, hexose monophosphate pathway activity arid ¹²⁵iodide fixation during phagocytosis. Further, myeloperoxidase (MPO) activity of patients’monocytes was comparable to the activity of control leucocytes. Using the Rebuck skin window, very few of the patients’mononuclcar cells were seen to migrate during the initial 2–4 hr of observation. During this time, the PMN migration of controls was maximal. Following the relatively acellular period observed in patients, a brisk mononuclear cell infiltration occurred apparently independent of the presence of neutrophils. Epinephrine injection into patients stimulated a marked increase of blood monocytes, suggesting the existence of a marginal monocyte pool. An injection of hydrocortisone caused an unexplained 3–8‐fold decrease in circulating monocytes. The delay of phagocytic cell migration to an inflammatory site, and the apparent sensitivity of monocytes to hydrocortisone may account in part for the increased susceptibility to infection in patients with severe congenital neutropenia.