Blood monocytes (MC) were isolated from alcoholics and from age-matched controls. Phagocytosis mediated by the IgG Fc-receptor (Fc-R) was assessed in the MC immediately after isolation by using IgG-opsonized sheep erythrocytes as test particles. Experiments were also performed after preincubating the MC in medium containing 10% autologous serum with or without ethanol (80 mM) in vitro at 37 degrees C for 15 min, and with or without ethanol (80 mM) present during the internalization assay in vitro (37 degrees C for 60 min). MC from alcoholics exhibited lower phagocytic capacity via the Fc-R than MC from healthy controls, approximately 50% versus 70% phagocytosing cells. Preincubation of the MC in medium containing 10% autologous serum with 80 mM ethanol, reduced the percentage of phagocytosing MC from controls to 55%, whereas no further reduction occurred in cells from alcoholics. When present during the assays of Fc-R function, ethanol decreased MC phagocytosis of IgG-coated particles significantly in both test groups, to about 30% phagocytosing cells. Blood samples disclosed increased serum levels of markers of liver dysfunction, immunoglobulins, increased sedimentation rate, and white blood cell counts among the alcoholics, while their serum levels of 1,25-dihydroxyvitamin D3 were reduced.