Mechanism of splenic immunosuppression during sepsis: key role of Kupffer cell mediators

Studies indicate that the liver, in particular the Kupffer cells, appear to be key contributors in the systemic inflammatory mediator response associated with shock and sepsis. Although several of these agents have been implicated as mediators of depressed immunoresponsiveness observed during sepsis, it remains unknown whether or not mediators released specifically by Kupffer cells play any significant role in producing the cellular dysfunction in distant organs. The aim of this study, therefore, was to determine whether or not acute Kupffer cell reduction before the onset of sepsis would protect splenic lymphocyte function. Kupffer cell number was reduced by prior (48 hours) treatment of mice with gadolinium chloride (GdCl2, 10 mg/kg of body weight, intravenously) or saline vehicle. Animals were then subjected to either sham-CLP (sham) or polymicrobial sepsis in the form of cecal ligation and puncture (CLP). Plasma and splenocytes were harvested at 2 or 24 hours after CLP. Splenocyte cultures were exposed to 2.5 micrograms concanavalin A/mL to assess their ability to release lymphokines. Cytokine (interleukin (IL)-2, IL-6, interferon-gamma, tumor necrosis factor-alpha) concentration in plasma or cell supernatants was assessed by bioassay. The results indicated that GdCl2 treated mice exhibited a marked reduction in circulating IL-6 levels at both 2 and 24 hours after CLP. Furthermore, the reduction of Kupffer cell number before the onset of sepsis completely prevented the depression of splenocyte IL-2 and interferon-gamma release, capacity. Thus mediators released by Kupffer cells during the systemic inflammatory response to polymicrobial sepsis play a significant role in producing immune dysfunction in resident splenic lymphocytes. In view of this, it appears that modulation of Kupffer cell hyperactivity during sepsis may be a novel approach for maintaining distant organ host defense mechanisms.