['Cytokines are essential for the prevention of microbial infections. Total parenteral nutrition (TPN) in infancy is associated with an increased risk of infection, and this could be related to altered cytokine production. The aim of the study was to determine if cytokine production is altered in monocytes from surgical infants receiving TPN.', 'There were 3 study groups: (a) infants receiving TPN, (b) enterally fed healthy control infants, and (c) enterally fed healthy control adults. Blood samples were incubated with either Escherichia coli LPS, Staphylococcus epidermidis, or with medium alone. Flow cytometry was used to measure monocyte intracellular cytokine: tumor necrosis factor (TNF)-alpha, interleukin (IL)-6, IL-1beta.', 'After LPS stimulation, the percent of monocytes producing TNF-alpha and IL-6 were lower in infants on TPN than both control infants and adults. This was most apparent for TNF-alpha. The difference for IL-1beta was significant only between infant on TPN and control adults. When blood was stimulated with S. epidermidis, all 3 cytokines were significantly lower in the TPN group compared with control adults. However, the differences between infants on TPN and infant controls only reached statistical significance for IL-6.'] Do surgical infants on total parenteral nutrition have impaired cytokine responses to microbial challenge?