Fig. 2. Concanavalin-A–stimulated production of T_H1 and T_H2 cytokines by peripheral blood mononuclear cells in control () and alcoholic (•) African American subjects. The ratio of the T_H1 to T_H2 was determined by dividing the T_H1 cytokine IFN- by the T_H2 cytokine IL-10. A sig-nificant group by time interaction was found (F(2,42) = 4.1, p < .02). The T_H1/T_H2 ratio increased from 03:00 to 06:30 hours (p < .01) in the controls, whereas the IFN-/IL-10 ratio decreased from 23:00 to 03:00 hours (p < .05) and remained low from 03:00 to 06:30 hours in the alcoholics.