• G Y Song, C S Chung, I H Chaudry, and A Ayala.
• Center for Surgical Research and Department of Surgery, Brown University School of Medicine and Rhode Island Hospital, Providence, 02903, USA.
• Surgery. 2000 Aug 1;128(2):133-8.

BackgroundAlthough studies have shown that there is a marked depression in cell-mediated (T(H)(1)) immunity after the onset of sepsis, the mechanism by which this occurs remains unknown. In this regard, the T(H2) cytokine IL-4 is known to regulate T(H1) and T(H2) cell responsiveness primarily through the activation of the signal transducer and activation of transcription factor-6 (Stat6) pathway.MethodsWe hypothesized that IL-4 may contribute to the suppression of cell-mediated immunity and to death seen in sepsis and that IL-4 may be acting through the Stat6 pathway. To determine this, we induced cecal ligation and puncture (CLP) or sham-CLP in male BALB/c mice. Mice received 2 mg of monoclonal antibody against IL-4 or IgG control at 12 hours after CLP (ie, at the onset of immune suppression). Splenic T cells were then isolated 24 hours after CLP and stimulated with monoclonal antibody to CD3. Cytokine release and Stat6 phosphorylation (activation) were determined. In a separate group of animals, survival was assessed over 10 days.ResultsThe results indicate that after CLP, T cells are suppressed in their ability to release the T(H1) cytokines, IL-2 and IFN-gamma. Alternatively, the release of T(H2) cytokines IL-10 and IL-4 is markedly increased after CLP. This was associated with an increase in phosphorylated Stat6 protein. In vivo treatment of mice with monoclonal antibody to IL-4 at 12 hours after CLP restores T(H1) responsiveness while preventing the increase in T(H2) cytokine release and Stat6 phosphorylation. Furthermore, neutralization of IL-4 markedly increased the survival rates in septic animals.ConclusionsTaken together, these data indicate that the T(H2) cytokine IL-4 contributes to the suppression of cell-mediated immunity and death associated with polymicrobial sepsis and suggest that IL-4 may be acting through the Stat6 pathway in septic animals.

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