Monocyte function in human neonates.

Monocytes of healthy, full-term newborns were isolated from cord blood, and functional and biochemical activities were quantitated. The yield of monocytes per milliliter of cord blood was 60% greater than that from the peripheral blood of healthy adults. Placental monocytes were initially less well spread than cells from adults, but no other morphological differences were noted. During 4 days of in vitro cultivation, placental monocytes secreted lysozyme at a constant rate, lost peroxidase activity, and increased 5'-nucleotidase activity 15- to 25-fold. Similar findings were obtained with monocytes from adults. Placental monocytes also displayed Fc and complement receptor activity. Ingestion and intracellular multiplication of Toxoplasma gondii were identical in normal placental and adult monocytes. Furthermore, toxoplasma multiplication was significantly inhibited by cells from both sources when the monocytes were preincubated with supernatants prepared from sensitized lymphocytes and toxoplasma antigen. Monocytes from newborns were competent cells in terms of the specific functions and activities we examined.