No abstract

The lipopolysaccharide (LPS) of enterohemorrhagic Escherichia coli (EHEC) and Shiga toxin together substantially contribute to the pathophysiology of typical hemolytic-uremic syndrome (HUS). Both factors have been shown to be immune stimulators and could play a key role in the individual innate immune response, characterized by proinflammatory and anti-inflammatory cytokines. By use of a whole blood stimulation model, we therefore compared the LPS-and superantigen-induced cytokine responses in children who had been having recovering from an acute episode of typical HUS for at least 6 months (group 1) with those in controls, who consisted of patients seen in the pediatric neurology outpatient department for routine examination (group 2). Samples were analyzed for cytokine protein levels and the levels of mRNA production. LPS stimulation revealed lower levels of interleukin 10 (IL-10) (P < 0.05) and increased levels of gamma interferon (P < 0.05) and increased ratios of pro-and anti-inflammatory cytokines (P < 0.05 for the IL-1␤/IL-10 ratio; P < 0.05 for the tumor necrosis factor alpha/IL-10 ratio) in group 1. In addition superantigen stimulation showed decreased IL-2 levels in group 1 (P < 0.01). Our results suggest an alteration of the cytokine response characterized by high proinflammatory cytokine levels and low anti-inflammatory cytokine levels as well as low levels of IL-2 production in children who have experienced an episode of typical HUS. We hypothesize that this altered immune response is not a residual effect of the infection but a preexisting characteristic of the patient. This could be one reason why individuals infected with EHEC are potentially predisposed to a systemic disease (HUS).In recent years our understanding of the pathophysiology of hemolytic-uremic syndrome (HUS) has further improved. However, the exact mechanisms leading to typical HUS (Dϩ HUS, where Dϩ is gastroenteritis positive) secondary to infection with enterohemorrhagic Escherichia coli (EHEC) are still not completely understood. As HUS is a disease of young children and elderly adults, a substantial role of the immune system has been discussed (6,12,13,19). It is well known that tumor necrosis factor alpha (TNF-␣) and Shiga toxin (Stx) potentiate the toxicity of each other for endothelial cells (9,20) and that elevated levels of antibodies to EHEC lipopolysaccharide (LPS) can be found in HUS patients (1, 3, 22). Therefore, a crucial role of the inflammation system has been suggested in HUS. Nevertheless, attempts to prove that patients with an acute episode of HUS have elevated systemic proinflammatory cytokine levels in comparison to those in children with infectious diarrhea have failed (8). Consequently, we and other groups recently added evaluation of anti-inflammatory cytokine profiles to the study design in order to monitor the balance between pro-and anti-inflammatory immune activation (10, 15, 24). We and others observed alterations in antiinflammatory cytokine levels, even though the results are conflicting: in our Dϩ H...

Rejection of vascularized allografts still poses the major problem in organ transplantation. Therefore, transplant rejection of cardiac allografts was investigated in a rat model (BN-to-LEW) under alpha/beta-TCR (R73) mAb-targeted therapy. Two protocols were studied: posttransplant ("immunosuppressive") and pretransplant conditioning therapy. In posttransplant therapy over a wide dose range, R73 mAb only marginally improved cardiac allograft survival (7.8 +/- 0.8 days vs. 12.5 +/- 0.8 days at 0.1 mg/kg for 7 days). In contrast, conditioning treatment with low-dose (0.1 mg/kg) anti-alpha/beta-TCR mAb given 3 to 7 days prior to organ transplantation was highly effective and resulted in 50% permanent acceptance of cardiac allografts. R73 mAb-treated rats were monitored with respect to peripheral lymphocyte populations and intragraft cytokine levels. A temporary, incomplete reduction (CD5+ cells) and partial modulation (alpha/beta-TCR/CD5 double+ cells) in the peripheral blood was observed. In contrast to untreated controls, intragraft production of IL-2 and IFN-gamma at the mRNA and protein level was abolished in both post- and pretreated recipients. Interestingly, pretransplant mAb application was associated with augmented in situ elaboration of the Th2-type cytokines, IL-4 and IL-10, together with up-regulated TGF-beta and PGE. Increased expression of IL-4 and IL-10 continued to be observed in long-term surviving allografts. In conclusion, the mechanism of conditioning therapy with alpha/beta-TCR mAb prior to alloantigen exposure appears to be a switch from Th1 to Th2 response allowing long-term acceptance of allogeneic grafts.

No abstract