Priscilla F. McAuliffe

Increased Natural CD4+CD25+ Regulatory T Cells and Their Suppressor Activity Do Not Contribute to Mortality in Murine Polymicrobial Sepsis

Regulatory T cells (Tregs), including natural CD4+CD25+ Tregs and inducible IL-10 producing T regulatory type 1 (TR1) cells, maintain tolerance and inhibit autoimmunity. Recently, increased percentages of Tregs have been observed in the blood of septic patients, and ex vivo-activated Tregs were shown to prevent polymicrobial sepsis mortality. Whether endogenous Tregs contribute to sepsis outcome remains unclear. Polymicrobial sepsis, induced by cecal ligation and puncture, caused an increased number of splenic Tregs compared with sham-treated mice. Splenic CD4+CD25+ T cells from septic mice expressed higher levels of Foxp3 mRNA and were more efficient suppressors of CD4+CD25− T effector cell proliferation. Isolated CD4+ T cells from septic mice displayed increased intracellular IL-10 staining following stimulation, indicating that TR1 cells may also be elevated in sepsis. Surprisingly, Ab depletion of total CD4+ or CD4+CD25+ populations did not affect mortality. Furthermore, no difference in survival outcome was found between CD25 or IL-10 null mice and wild-type littermates, indicating that Treg or TR1-generated IL-10 are not required for survival. These results demonstrate that, although sepsis causes a relative increase in Treg number and increases their suppressive function, their presence does not contribute significantly to overall survival in this model.

CD11c+ Dendritic Cells Are Required for Survival in Murine Polymicrobial Sepsis

CD11c+ dendritic cells (DCs) are APCs that link innate and adaptive immunity. Although DCs are lost from spleen and lymph nodes in sepsis, their role in outcome remains unclear. Transgenic mice (B6.FVB-Tg.Itgax-DTR/EGFP.57Lan/J) expressing the diphtheria toxin (DT) receptor on the CD11c promoter (DCKO mice) received 4 ng/kg DT, which resulted in depletion of 88–95% of mature myeloid and lymphoid DCs, with less depletion (75%) of plasmacytoid DCs. Pretreatment of DCKO mice with DT resulted in reduced survival in sepsis compared with saline-pretreated DCKO mice (0 vs 54%; p < 0.05) or DT-treated wild-type littermates (0 vs 54%; p < 0.05). This increased mortality was not associated with either increased bacteremia or plasma cytokine concentrations. Intravenous injection of 107 wild-type DCs improved survival in DCKO mice (42 vs 0%; p = 0.05). These data confirm that DCs are essential in the septic response and suggest that strategies to maintain DC numbers or function may improve outcome.

Bacillus cereus Necrotizing Fasciitis in a Patient with End-Stage Liver Disease

BACKGROUND Bacillus cereus has been increasingly recognized as a virulent pathogen, particularly in immunocompromised patients. METHODS Presented is a case report of a 24-year-old man with end-stage liver disease secondary to primary sclerosing cholangitis, who developed necrotizing fasciitis of the right lower leg due to B. cereus. The bacterium isolated from the patient was compared with environmental strains for quantity of secreted proteins as well as hemolytic and cytotoxic activities. RESULT Despite above-the-knee amputation and aggressive antibiotic therapy, the patient expired on hospital day 13. The patient isolate demonstrated a protein secretion pattern and cytotoxicity similar to those of an environmental strain known to produce exotoxins. However, the isolate did produce a larger ratio of zone of hemolysis to colony size on blood agar plates compared with the environmental strain. CONCLUSION To the best of our knowledge, this is the only report of B. cereus as the etiology of necrotizing fasciitis in a patient with end-stage liver disease. Because the infecting bacterium correlates with the environmental strain, the severity of the patients disease is likely related to his immunocompromised state. Therefore, B. cereus should be considered a potential pathogen rather than a contaminant.

Major hepatectomy induces phenotypic changes in circulating dendritic cells and monocytes.

IntroductionPatients undergoing major hepatectomy are at increased risk for post-operative morbidity and mortality, and changes in the phenotype of effector cells may predispose these patients to infectious sequelae.MethodsTo better understand post-hepatectomy immune responses, peripheral blood from 15 hepatectomy patients was drawn immediately before and after liver resection and on post-operative days 1, 3, and 5. Circulating monocytes and dendritic cells were analyzed by flow cytometry for quantity, phenotype, activation status, human leukocyte antigen DR (HLA-DR) expression, and toll-like receptor-2 and -4 expression.ResultsMajor hepatectomy increased the numbers of activated CD16bright blood monocytes and the percentage of activated dendritic cells, although monocyte HLA-DR expression was reduced. These results may represent both dysfunctional antigen presentation and pending anergy, as well as cellular priming of immune effector cells. Better understanding of the alterations in innate immunity induced by hepatectomy may identify strategies to reduce infectious outcomes.

Varying Blood Monocyte and Dendritic Cell Responses after Laparoscopic Versus Open Gastric Bypass Surgery

Background: Laparoscopy may activate innate immunity less than conventional open surgery. This may be important in obese patients who have pre-existing low-grade inflammation. This study examined phenotypic changes in blood monocytes (Mcs) and dendritic cells (DCs) from patients undergoing laparoscopic (L) or open (O) Roux-en-Y gastric bypass (RYGBP) surgery. Methods: 8 patients (3 male) had blood drawn before and after RYGBP, and on postoperative day (POD) 1, 3, and 28. Mc and DC quantity, phenotype, and activation status were determined by flow cytometry. Results: Mean BMI was 53 ± 4 and 46 ± 1, and length of stay was 6.3 ± 3.2 and 3.5 ± 0.6 days, in the O (n=4) versus L (n=4) groups, respectively. Postoperative WBC count was 16 ± 1 × 103/mm3 after O and 10 ± 1 × 103/mm3 after LRYGBP (P<0.001). This was due to a greater rise in neutrophils and decline in lymphocytes after ORYGBP (P<0.001). Total Mcs increased in both groups at POD 1, but the number of CD18+ Mcs was reduced after ORYGBP (P=0.04). Mc human leukocyte antigen (HLA)-DR expression was lower in CD16+ Mcs after ORYGBP, suggesting decreased capacity to present antigen (P=0.002). Postoperatively, total DCs decreased in both groups, but recovered (P=0.04). The proportion and activation of the tolerogenic DC2 phenotype was lower, whereas the percentage of the ldDC phenotype was higher, in the O group (P=0.006). Conclusion: RYGBP changes the quantity and phenotype of circulating blood Mcs and DCs. Although there were overall similarities in the overall response to gastric surgery between open and laparoscopic, there were some notable differences, including a greater reduction in HLA-DR expression and increased number of immature DCs in the ORYGBP group. The findings suggest that RYGBP may have varying immunologic consequences depending upon the surgical procedure employed.