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The Role of TLR2 and TLR4 in Recognition and Uptake of the Apicomplexan Parasite <i>Eimeria bovis</i> and Their Effects on NET Formation
oleh: Tamara Muñoz-Caro, Amanda J. Gibson, Iván Conejeros, Dirk Werling, Anja Taubert, Carlos Hermosilla
Format: | Article |
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Diterbitkan: | MDPI AG 2021-01-01 |
Deskripsi
Background: Bovine polymorphonuclear neutrophils (PMN) constitutively express the Toll-like receptors (TLRs) TLR2 and TLR4 and have been shown to generate Neutrophil extracellular traps (NETs) upon exposure to <i>Eimeria bovis</i>. The present work investigated the role of TLR2 and TLR4 in the recognition and uptake of <i>E. bovis</i> sporozoites, IL-8 production and neutrophil extracellular trap (NET) formation. Methods: TLR expression was performed by flow cytometric analysis on PMN exposed to live carboxyfluorescein succinimidyl ester (CFSE)-stained sporozoites. Supernatants of PMN exposed to different <i>E. bovis</i> sporozoite preparations and antigens in the absence or presence of TLR antibodies were assessed for IL-8 secretion. Cells were exposed to sporozoite preparations and assessed for the activation of transcription factor NF-κB using a luciferase reporter assay. Immunofluorescence analysis was done to investigate TLR2 and TLR4 surface expression and NET formation on bovine PMN exposed to vital sporozoites. Results: we observed significantly increased TLR2 and TLR4 expression with a mean increase in expression that was greater for TLR2 than TLR4. This upregulation neither inhibited nor promoted sporozoite phagocytosis by bovine PMN. Live sporozoites together with anti-TLR2 mAb resulted in a significant enhancement of IL-8 production. NF-κB activation was more strongly induced in TLR2-HEK cells than in TLR4/MD2-HEK cells exposed to heat-killed sporozoites and antigens. Immunofluorescence analysis showed TLR-positive signals on the surface of PMN and concomitant NET formation. Conclusions: This is the first report on <i>E. bovis</i>-induced concomitant TLR2 and TLR4 expression during bovine PMN-derived NETosis.