The in vitro effect of cefotaxime on the production of interleukin (IL)-1β, IL-2, IL-6 and tumor necrosis factor α (TNFα) was studied in term neonates and was compared with that of adults. The addition of cefotaxime caused a significant enhancement of IL-2 production by cells of both adults and neonates, and increased the secretion of TNFα by peripheral blood mononuclear cells (PBMC) of adults, whereas the synthesis of this cytokine by cord blood mononuclear cells (CBMC) of the newborns was not affected. In contrast with the described stimulatory effects of cefotaxime, this drug induced dose-dependent inhibition of the spontaneous and lipopolysaccharide (LPS)-induced IL-1β production by cells of the two groups, but had no effect on the in vitro production of IL-6. These data suggest that cefotaxime, apart from its known antimicrobial activity, may modify the host immune response of both newborns and adults, via the alteration of cytokine production. (C) 2000 Editions scientifiques et medicales Elsevier SAS.