PLB-985 Neutrophil-Like Cells as a Model To Study Aspergillus fumigatus Pathogenesis

Polymorphonuclear leukocytes are an important defense against human fungal pathogens, yet our model systems to study this group of cells remain very limited in scope. In this study, we established that differentiated PLB-985 cells can serve as a model to recapitulate several important aspects of human polymorphonuclear leukocyte interactions with the important human fungal pathogen Aspergillus fumigatus .

Yersinia pestis Type III Secretion System-Dependent Inhibition of Human Polymorphonuclear Leukocyte Function

ABSTRACT Human polymorphonuclear leukocytes (PMNs, or neutrophils) are the primary innate host defense against invading bacterial pathogens. Neutrophils are rapidly recruited to sites of infection and ingest microorganisms through a process known as phagocytosis. Following phagocytosis by human PMNs, microorganisms are killed by reactive oxygen species (ROS) and microbicidal products contained within granules. Yersinia pestis, the causative agent of plague, is capable of rapid replication and dissemination from sites of infection in the host. Although Y. pestis survives in macrophages, the bacterial fate following interaction with human PMNs is less clear. The ability of Y. pestis to inhibit phagocytosis by human PMNs was assessed by differential fluorescence microscopy and was shown to be dependent on expression of the type III secretion system (TTSS). Previous studies have demonstrated that TTSS expression in enteropathogenic Yersinia spp. also inhibits the respiratory burst in PMNs and macrophages, and we show here that human PMN ROS production is similarly repressed by Y. pestis. However, exclusion of uningested TTSS-expressing Y. pestis with gentamicin revealed that intracellular bacteria are eliminated by human PMNs, similar to bacteria lacking the TTSS. In summary, our results suggest that the Y. pestis TTSS contributes to extracellular survival following interactions with human PMNs and that the intracellular fate is independent of TTSS inhibition of neutrophil ROS production.

Inhibition by soya isoflavones of human polymorphonuclear leukocyte function: possible relevance for the beneficial effects of soya intake

Lower CVD incidence is reported in Asian populations consuming soya-containing food. As polymorphonuclear leukocytes (PMN) are involved in the risk of CVD, we investigated the modulatory effect of soya isoflavones on several PMN functions and their molecular mechanismsin vitro. PMN, isolated from blood from healthy subjects, were tested upon activation with 1 μm- n-formyl-methyl-leucyl-phenylalanine (fMLP) for superoxide anion production (ferric cytochrome c reduction) and released elastase (chromogenic test). PMN homotypic aggregates stimulated by fMLP or P-selectin in dynamic conditions were detected by optical microscopy. PMN, mixed with thrombin-activated, washed platelets, formed cell aggregates, measured by flow cytometry. Phosphorylation of Pyk2, a focal adhesion kinase, was studied by immunoprecipitation and immunoblotting with specific antibodies. Genistein, daidzein and equol inhibited superoxide anion production (IC500·25 (sem0·1), 21·0 (sem4·2) and 13·0 (sem2·8) μm, respectively); the release of elastase was prevented by genistein (IC5063 (sem17) μm). PMN homotypic aggregates, stimulated by fMLP, were significantly reduced (24 (sem12) and 51 (sem14) % of control) by 100 μmgenistein and equol. P-selectin-induced aggregates were reduced to 19 (sem6), 44 (sem10) and 28 (sem9) % of control by 100 μmgenistein, daidzein and equol, respectively. Genistein, daidzein and equol also significantly reduced mixed platelet-PMN aggregates (IC504·0 (sem0·9), 57 (sem6) and 66 (sem23) μm, respectively). In PMN challenged by fMLP or P-selectin, activation of Pyk2 was prevented by isoflavones. The cardioprotective effect of soya-containing food might be linked to reduction of PMN activation and PMN-platelet interaction, novel targets for the biological effects of soya isoflavones.