c Myeloid-derived suppressor cells (MDSCs) are a heterogeneous Gr1؉ CD11b ؉ population of immature cells containing granulocytic and monocytic progenitors, which expand under nearly all inflammatory conditions and are potent repressors of T-cell responses. Studies of MDSCs during inflammatory responses, including sepsis, suggest they can protect or injure. Here, we investigated MDSCs during early and late sepsis. To do this, we used our published murine model of cecal ligation and puncture (CLP)-induced polymicrobial sepsis, which transitions from an early proinflammatory phase to a late anti-inflammatory and immunosuppressive phase. We confirmed that Gr1 ؉ CD11b ؉ MDSCs gradually increase after CLP, reaching ϳ88% of the bone marrow myeloid series in late sepsis. Adoptive transfer of early (day 3) MDSCs from septic mice into naive mice after CLP increased proinflammatory cytokine production, decreased peritoneal bacterial growth, and increased early mortality. Conversely, transfer of late (day 12) MDSCs from septic mice had the opposite effects. Early and late MDSCs studied ex vivo also differed in their inflammatory phenotypes. Early MDSCs expressed nitric oxide and proinflammatory cytokines, whereas late MDSCs expressed arginase activity and anti-inflammatory interleukin 10 (IL-10) and transforming growth factor ␤ (TGF-␤). Late MDSCs had more immature CD31؉ myeloid progenitors and, when treated ex vivo with granulocyte-macrophage colony-stimulating factor (GM-CSF), generated fewer macrophages and dendritic cells than early MDSCs. We conclude that as the sepsis inflammatory process progresses, the heterogeneous MDSCs shift to a more immature state and from being proinflammatory to anti-inflammatory.

Aims-To investigate the prevalence of Helicobacterpylori in the saliva ofpatients infected with this bacterium. Methods-A novel polymerase chain reaction (PCR) assay was developed to detect Hpylori in saliva and gastric biopsy specimens from patients undergoing endoscopy. Results-Our PCR assay amplified a 417 base pair fragment of DNA from all 21DNAs derived from H pylon clinical isolates but did not amplify DNA from 23 non-H pylon strains. Sixty three frozen gastric biopsy and 56 saliva specimens were tested. H pylon specific DNA was detected by PCR in all 39 culture positive biopsy specimens and was also identified from another seven biopsy specimens which were negative by culture but positive by histology. H pylon specific DNA was identified by PCR in saliva specimens from 30 (75%) of 40 patients with H pylori infection demonstrated by culture or histological examination, or both, and in three patients without H pylon infection in the stomach. Conclusion-The results indicate that the oral cavity harbours H pylon and may be the source of infection and transmission. (J Clin Pathol 1995;48:662-666)

The sepsis initial hyperinflammatory reaction, if not treated early, shifts to a protracted state of immunosuppression that alters both innate and adaptive immunity and is associated with elevated mortality. Myeloid-derived suppressor cells (MDSCs) are myeloid progenitors and precursors that fail to differentiate into mature innate-immunity cells and are known for their potent immunosuppressive activities. We previously reported that murine MDSCs expand dramatically in the bone marrow during late sepsis, induced by cecal ligation and puncture, and demonstrated that they contribute to late-sepsis immunosuppression. However, the molecular mechanism responsible for generating these immature Gr1 ؉ CD11b ؉ myeloid cells during sepsis remains unknown. We show here that sepsis generates a microRNA (miRNA) signature that expands MDSCs. We found that miRNA 21 (miR-21) and miR-181b expression is upregulated in early sepsis and sustained in late sepsis. Importantly, we found that simultaneous in vivo blockade of both miRNAs via antagomiR (a chemically modified miRNA inhibitor) injection after sepsis initiation decreased the bone marrow Gr1 ؉ CD11b ؉ myeloid progenitors, improved bacterial clearance, and reduced late-sepsis mortality by 74%. Gr1 ؉ CD11b ؉ cells isolated from mice injected with antagomiRs were able to differentiate ex vivo into macrophages and dendritic cells and produced smaller amounts of the immunosuppressive interleukin 10 (IL-10) and transforming growth factor ␤ (TGF-␤) after stimulation with bacterial lipopolysaccharide, suggesting that immature myeloid cells regained their maturation potential and have lost their immunosuppressive activity. In addition, we found that the protein level of transcription factor NFI-A, which plays a role in myeloid cell differentiation, was increased during sepsis and that antagomiR injection reduced its expression. Moreover, knockdown of NFI-A in the Gr1 ؉ CD11b ؉ cells isolated from late-septic mice increased their maturation potential and reduced their production of the immunosuppressive mediators, similar to antagomiR injection. These data support the hypothesis that sepsis reprograms myeloid cells and thus alters the innate immunity cell repertoire to promote immunosuppression, and they demonstrate that this process can be reversed by targeting miR-21 and miR181b to improve late-sepsis survival.

Sepsis progresses from an early/acute hyperinflammatory to a late/chronic hypoinflammatory phase with immunosuppression. As a result of this phenotypic switch, mortality in late sepsis from persistent primary infection or opportunistic new infection often exceeds that in acute sepsis. Emerging data support that persistence of the hypoinflammatory (hyporesponsive) effector immune cells during late sepsis might involve alterations in myeloid differentiation/maturation that generate circulating repressor macrophages that do not readily clear active infection. Here, we used a cecal ligation and puncture (CLP) murine model of prolonged sepsis to show that adoptive transfer of CD34 ؉ hematopoietic stem-progenitor cells after CLP improves long-term survival by 65%. CD34 ؉ cell transfer corrected the immunosuppression of late sepsis by (i) producing significantly higher levels of proinflammatory mediators upon ex vivo stimulation with the Toll-like receptor 4 (TLR4) agonist lipopolysaccharide, (ii) enhancing phagocytic activity of peritoneal macrophages, and (iii) clearing bacterial peritonitis. Improved immunity by CD34 ؉ cell transfer decreased inflammatory peritoneal exudate of surviving late-sepsis mice. Cell tracking experiments showed that the transferred CD34 ؉ cells first appeared in the bone marrow and then homed to the spleen and peritoneum. Because CD34 ؉ cells did not affect the early-phase hyperinflammatory response, it is likely that the newly incorporated pluripotent CD34 ؉ cells differentiated into competent immune cells in blood and tissue, thereby reversing or replacing the hyporesponsive endotoxintolerant cells that occur and persist after the initiation of early sepsis. Sepsis is a major clinical problem (9, 52), with more than a 40% mortality rate, and is the leading cause of death in intensive care units (5,17). Evidence supports that the pathophysiology of sepsis varies as it moves from an initiating early/acute hyperinflammatory phase to a late/chronic hypoinflammatory and immunosuppressive phase (31,47,51,67). The early phase of sepsis is typified by a systemic inflammatory response syndrome (SIRS) characterized by excessive production of proinflammatory mediators by neutrophils and macrophages (53), increased generation of reactive oxygen species, and leukocyte-induced microvascular injury and organ failure (35). These destructive inflammatory responses occur in human (28) and animal (46, 51) sepsis, producing multiorgan dysfunction.While the early systemic inflammatory reaction of sepsis often spans several days (47, 61) and is considered a normal defense, the transition to a compensatory anti-inflammatory response syndrome (sometimes called CARS) to limit damage generates immunosuppression and promotes chronic infection (6, 12). CARS is characterized by downregulation in the ability of leukocytes to express proinflammatory mediators, impaired phagocytic capacity of neutrophils and macrophages (33,40,50), and significant apoptosis of lymphocytes and dendritic cells (16,29). Previous studies ha...

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