SummaryThe capacity of peripheral blood mononuclear cells (PBMCs) of anorexia nervosa (AN) patients to produce interleukin-1 (IL-1), interleukin-2 (IL-2), and interleukin-3-like activity (IL-3-LA) was studied. A significantly lower (−49%, p < 0.005) capacity to synthesize IL-2 and an almost significantly impaired ability (−35%, p = 0.058) to release IL-3-LA by PBMCs of AN patients was found, as compared with cells of the control group. IL-1 production, either spontaneous or after stimulation with lipopolysaccharide (LPS), did not differ significantly between AN patients and healthy subjects. The lessened capacity to produce IL-2 was accompanied by an enhanced stimulatory activity of the patient sera on the production of this cytokine by PBMCs of healthy subjects. It is therefore suggested that the serum of AN patients contains a stimulatory factor or factors for cytokine production that compensates for the lower production of cytokines by AN PBMCs. Such a compensatory mechanism may explain why AN patients do not have an higher susceptibility to infections.