Functional and phenotypic changes associated with the in vitro development of human monocytes into activated macrophages

Freshly isolated human peripheral blood monocytes had minimal cytotoxic effect in vitro on the schistosomula of Schistosoma mansoni. However, stimulation of the cells with either interferon gamma (IFN) or specific anti-parasite antiserum caused an increase in cytotoxicity. Additionally, the normal development of monocytes into macrophages over 7 days was associated with a sharp increase in cytotoxicity. The non-cytotoxic monocytes were compared with activated macrophages to assess whether cytotoxicity was associated with changes in immunophenotype. As monocytes developed into macrophages there were marked increases in transferrin receptors (HB21), macrophage cellular integrin (3.9), and Fc receptors (KB61). A further three markers showed increased expression in 7-day-old macrophages stimulated by IFN, namely a high affinity Fc gamma receptor (10.1), MHC Class II (1B5) and tumour necrosis factor (TNF).