Interleukin (IL) 13 is an anti-inflammatory cytokine that reduces inflammatory cytokine production, and enhances monocyte survival and MHC class II and CD23 expression. The only report of IL-13 in human sepsis noted no increase in IL-13 concentration, in contrast to animal data. This study further examined the expression of IL-13 in relation to human sepsis.

In a prospective observational study of 31 patients (24 men) with sepsis or septic shock, high-sensitivity enzyme-linked immunoabsorbent assay (ELISA) was used to quantify levels of tumour necrosis factor (TNF) α on admission, and on days 1, 3, 5 and 7 thereafter. IL-13 and IL-2 were assayed by standard ELISA, and HLA-DR on CD14-positive monocytes was measured by flow cytometry.

Twenty-three patients developed septic shock. Monocyte HLA-DR levels showed greater depression and a slower recovery in shocked than non-shocked patients. The serum IL-13 concentration was significantly higher in the shocked group from admission to day 3, but subsequently decreased to levels similar to those in the non-shocked group. IL-13 concentrations were higher in non-survivors. The TNF-α concentration was higher in those with septic shock than in those without. The TNF-α level correlated with IL-13 concentration (r_S = 0·61, P = 0·002). The IL-13/TNF-α ratio was greater in patients with shock than those with sepsis only (P = 0·017). IL-2 was undetectable.

In human sepsis and septic shock, IL-13 correlated with TNF-α expression, but its effect on HLA-DR class II molecules remains unclear.