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Mycoplasma bovis ( M. bovis ) is a small bacterium that lacks a cell wall. M. bovis infection results in chronic pneumonia and polyarthritis syndrome (CPPS), otitis media, conjunctivitis, and meningitis in feedlot cattle and mastitis in dairy cattle. Numerous studies of peripheral mononuclear cells (PBMC) indicate that M. bovis evades host immunity through targeted effects on immune cell activity, including inhibition of effector function and simultaneous aberrant activation of immune cell activity that has no effect on protection against the bacterium. Few studies have addressed the interaction between M. bovis and neutrophils, one of the most important cell subsets of innate immunity. We hypothesized that M. bovis modifies specific neutrophil activities to support its persistence and systemic dissemination. In this study, we demonstrate that M. bovis enhances neutrophil apoptosis, stimulates production of pro-inflammatory cytokines, IL-12 and TNF-α, inhibits production of nitric oxide (NO) but augments elastase release. We also show that IL-17 an inflammatory cytokine produced by Th-17 cells does not enhance the capacity of neutrophils to destroy M. bovis . These findings present novel mechanisms of mycoplasma evasion of host innate immunity and provide potential opportunities for immuno-therapeutic interventions. [ABSTRACT FROM AUTHOR]

Abstract: Regulation of TLR responses is required in the intestine to prevent unnecessary responses to commensal microorganisms and maintain tissue homeostasis. Several mechanisms have been proposed for the regulation of TLR responses in intestinal epithelial and lamina propria cells. However, whether this regulation occurs in Peyer''s patches (PP) is not known. While investigating cellular responses to the TLR9 agonist CpG ODN, we observed that PP cells responded poorly to CpG ODN stimulation despite expressing TLR9. We hypothesized that PP cells produced the immunoregulatory cytokine IL-10 which suppressed TLR-induced cytokine responses. In vitro neutralization of IL-10 or depletion of CD21+ B cells from PP resulted in significant increases in IL-12, IFNγ and IFNα responses in PP cells stimulated with CpG ODN. Essentially, our investigation have identified a novel population of IL-10-secreting B cells in PP with regulatory functions (Bregs). These Bregs may play an important role in the maintenance of intestinal homeostasis. [Copyright &y& Elsevier]