Animal Health Department, NEIKER-Basque Institute for Agricultural Research and Development-Basque Research and Technology Allianca (BRTA), Derio, Spain.
Food Quality and Safety Department, Universidad del País Vasco/Euskal Herriko Unibertsitatea (UPV/EHU), Vitoria-Gasteiz, Spain.
Front Immunol. 2021 Mar 17;12:645304. doi: 10.3389/fimmu.2021.645304. eCollection 2021.
subsp. (Map) is the underlying pathogen causing bovine paratuberculosis (PTB), an enteric granulomatous disease that mainly affects ruminants and for which an effective treatment is needed. Macrophages are the primary target cells for Map, which survives and replicates intracellularly by inhibiting phagosome maturation. Neutrophils are present at disease sites during the early stages of the infection, but seem to be absent in the late stage, in contrast to healthy tissue. Although neutrophil activity has been reported to be impaired following Map infection, their role in PTB pathogenesis has not been fully defined. Neutrophils are capable of releasing extracellular traps consisting of extruded DNA and proteins that immobilize and kill microorganisms, but this mechanism has not been evaluated against Map. Our main objective was to study the interaction of neutrophils with macrophages during an mycobacterial infection. For this purpose, neutrophils and macrophages from the same animal were cultured alone or together in the presence of Map or Bacillus-Calmette-Guérin (BCG). Extracellular trap release, mycobacteria killing as well as IL-1β and IL-8 release were assessed. Neutrophils released extracellular traps against mycobacteria when cultured alone and in the presence of macrophages without direct cell contact, but resulted inhibited in direct contact. Macrophages were extremely efficient at killing BCG, but ineffective at killing Map. In contrast, neutrophils showed similar killing rates for both mycobacteria. Co-cultures infected with Map showed the expected killing effect of combining both cell types, whereas co-cultures infected with BCG showed a potentiated killing effect beyond the expected one, indicating a potential synergistic cooperation. In both cases, IL-1β and IL-8 levels were lower in co-cultures, suggestive of a reduced inflammatory reaction. These data indicate that cooperation of both cell types can be beneficial in terms of decreasing the inflammatory reaction while the effective elimination of Map can be compromised. These results suggest that neutrophils are effective at Map killing and can exert protective mechanisms against Map that seem to fail during PTB disease after the arrival of macrophages at the infection site.
亚种。(Map) 是引起牛副结核病 (PTB) 的潜在病原体，这是一种主要影响反刍动物的肠肉芽肿性疾病，需要有效的治疗方法。巨噬细胞是 Map 的主要靶细胞，它通过抑制吞噬体成熟在细胞内存活和复制。在感染的早期阶段，中性粒细胞存在于疾病部位，但在后期阶段似乎不存在，而在健康组织中则不存在。尽管已经报道 Map 感染后中性粒细胞的活性受损，但它们在 PTB 发病机制中的作用尚未完全确定。中性粒细胞能够释放由挤出的 DNA 和蛋白质组成的细胞外陷阱，这些陷阱可以固定和杀死微生物，但这种机制尚未针对 Map 进行评估。我们的主要目标是研究中性粒细胞与巨噬细胞在分枝杆菌感染过程中的相互作用。为此，在存在 Map 或卡介苗 (BCG) 的情况下，从同一动物中单独培养或共同培养中性粒细胞和巨噬细胞。评估细胞外陷阱的释放、分枝杆菌的杀伤以及 IL-1β 和 IL-8 的释放。当单独培养和在没有直接细胞接触的情况下与巨噬细胞共培养时，中性粒细胞会针对分枝杆菌释放细胞外陷阱，但在直接接触时受到抑制。巨噬细胞对 BCG 的杀伤效率极高，但对 Map 的杀伤效率却很低。相比之下，中性粒细胞对两种分枝杆菌的杀伤率相似。感染 Map 的共培养显示出两种细胞类型结合的预期杀伤效果，而感染 BCG 的共培养显示出超出预期的增强杀伤效果，表明存在潜在的协同合作。在这两种情况下，共培养物中的 IL-1β 和 IL-8 水平较低，提示炎症反应减轻。这些数据表明，两种细胞类型的合作在减轻炎症反应方面可能是有益的，而 Map 的有效消除可能会受到影响。这些结果表明，中性粒细胞对 Map 的杀伤有效，并能发挥针对 Map 的保护机制，但在巨噬细胞到达感染部位后，PTB 疾病中似乎会失效。
