Journal of leukocyte biology
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The causative microorganisms dictate the type of MDSC generated in sepsis patients, and a large proportion of PMN-MDSCs in gram-positive sepsis includes immunosuppressive myeloid blasts. MDSCs constitute a heterogeneous population of immature myeloid cells that potently suppress immune responses. They were identified originally in cancer patients and have since been reported to occur also in chronic inflammation, autoimmunity, and even bacterial infections. ⋯ We found a high frequency of typical CD14(+)HLA-DR(low) Mo-MDSCs in all sepsis patients, whereas the typical PMN-MDSCs, as well as a prominent CD14(low) PMN-MDSC-like population, appeared preferentially in gram-positive cases. The CD14(low) PMN-MDSC variant was demonstrated to suppress T cell proliferation in vitro via a ROS-dependent mechanism, to display an increased IL-10:TNF-α ratio, and to present with signs of immaturity: blast morphology and low cytokine levels. We conclude that a spectrum of cells with MDSC features is enriched in sepsis and that the microbial origin of sepsis contributes to the substantial interindividual patient variation in the MDSC pattern.
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The immunomodulatory effects of PD-1 and CD4(+)CD25(+) Tregs in the resolution of ALI are still poorly understood. Accordingly, 1 million Tregs were isolated from spleens of WT C57BL/6 or PD-1(-/-) mice (magnetical bead purification and subsequent labeling with/without Vybrant dye) and then AT into mice subjected to Hem shock during their resuscitation period, which were subsequently subjected to CLP/septic challenge (24 h post-Hem) to induce iALI. Initially, we demonstrated that Vybrant-labeled AT Tregs appear in the lungs of iALI mice. ⋯ ALI was exacerbated in these recipient mice receiving AT PD-1(-/-) Tregs to the same extent as iALI mice that did not receive Tregs. These data imply that Tregs can act directly to modify the innate immune response induced by experimental iALI, and this is mediated, in part, by PD-1. Hence, the manipulation of Tregs may represent a plausible target for treating iALI.
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Inflammatory pain is based on stimulation and sensitization of peripheral endings of sensory neurons (nociceptors) by pronociceptive mediators. These mediators can be released by resident cells, as well as invading immune cells. Although neutrophils are known to release various mediators, which can stimulate or sensitize nociceptors, the extent of their contribution to nociceptive responses is unclear. ⋯ The effects observed in HLB-219 mice were relatively small and not reproduced in vWF-deficient mice or after antibody-mediated blockage of GPIbα. Flow chamber and transmigration assays showed that platelets were not necessary for neutrophil adhesion to endothelial cells but increased their transmigration. Taken together, zymosan-induced mechanical allodynia is, in contrast to edema formation, independent of neutrophils, and recruitment of neutrophils is only partly influenced by interactions with platelets.
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LL-37/hCAP-18 is the only human member of the cathelicidin family and plays an important role in killing various pathogens, as well as in immune modulation. In this study, we investigated the effect of LL-37 on bacterial phagocytosis by macrophages and demonstrate that LL-37 enhances phagocytosis of IgG-opsonized Gram-negative and Gram-positive bacteria in a dose- and time-dependent manner by dTHP-1 cells. In addition, LL-37 enhanced phagocytosis of nonopsonized Escherichia coli by human macrophages. ⋯ However, TLR4 signaling was also coupled to the phagocytic response, as a specific TLR4 antibody significantly suppressed phagocytosis of IgG-opsonized E. coli and nonopsonized E. coli by dTHP-1 cells. Finally, macrophages from Cnlp(-/-) mice exhibited diminished bacterial phagocytosis compared with macrophages from their WT littermates. In conclusion, we demonstrate a novel, immune-modulatory mechanism of LL-37, which may contribute to bacterial clearance.
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ChrX cellular mosaicism for X-linked genetic polymorphisms in females versus the single ChrX representation in males denotes a genetic difference, which may contribute to gender bias in the inflammatory response. This hypothesis was tested in female F1 offspring of consomic mice (BL6J-ChrX(A/J)/NaJ) that were homokaryotic or mosaic for the active BL6 and AJ ChrXs or for IRAK1 deficiency linked to the BL6 ChrX. Sepsis was initiated by CLP. ⋯ Sepsis decreased cell ratios more in IRAK1-mosaic than in WT-mosaic mice. The study reveals functional variability in cellular mosaicism for IRAK1 expression and natural X-linked polymorphisms during sepsis. Mosaicism for IRAK1 expression is accompanied by skewing toward deficient immune cell populations, producing a phenotype that is preconditioned for improved sepsis outcome similar to that observed in IRAK1 deficiency.