Hussen Jamal, Schuberth Hans-Joachim
Department of Microbiology and Parasitology, College of Veterinary Medicine, King Faisal University, Al Ahsa, Hofuf, Saudi Arabia.
Immunology Unit, University of Veterinary Medicine, Hannover, Germany.
Front Immunol. 2017 Dec 19;8:1875. doi: 10.3389/fimmu.2017.01875. eCollection 2017.
Peripheral blood monocytes of several species can be divided into different subpopulations with distinct phenotypic and functional properties. Herein, we aim at reviewing published work regarding the heterogeneity of the recently characterized bovine monocyte subsets. As the heterogeneity of human blood monocytes was widely studied and reviewed, this work focuses on comparing bovine monocyte subsets with their human counterparts regarding their phenotype, adhesion and migration properties, inflammatory and antimicrobial functions, and their ability to interact with neutrophilic granulocytes. In addition, the differentiation of monocyte subsets into functionally polarized macrophages is discussed. Regarding phenotype and distribution in blood, bovine monocyte subsets share similarities with their human counterparts. However, many functional differences exist between monocyte subsets from the two species. In contrast to their pro-inflammatory functions in human, bovine non-classical monocytes show the lowest phagocytosis and reactive oxygen species generation capacity, an absent ability to produce the pro-inflammatory cytokine IL-1β after inflammasome activation, and do not have a role in the early recruitment of neutrophils into inflamed tissues. Classical and intermediate monocytes of both species also differ in their response toward major monocyte-attracting chemokines (CCL2 and CCL5) and neutrophil degranulation products (DGP) . Such differences between homologous monocyte subsets also extend to the development of monocyte-derived macrophages under the influence of chemokines like CCL5 and neutrophil DGP. Whereas the latter induce the differentiation of M1-polarized macrophages in human, bovine monocyte-derived macrophages develop a mixed M1/M2 macrophage phenotype. Although only a few bovine clinical trials analyzed the correlation between changes in monocyte composition and disease, they suggest that functional differences between human and bovine monocyte subsets are also reflected in their different clinical relevance for distinct diseases. In opposite to the human system, where higher blood cell number of non-classical monocytes was widely correlated with several human infectious and non-infectious diseases, higher counts of bovine intermediate monocytes are suggested as a potential biomarker for inflammatory responses postpartum.
几种物种的外周血单核细胞可分为具有不同表型和功能特性的不同亚群。在此，我们旨在综述已发表的关于最近鉴定的牛单核细胞亚群异质性的研究工作。由于人类血液单核细胞的异质性已得到广泛研究和综述，本工作重点比较牛单核细胞亚群与其人类对应物在表型、黏附与迁移特性、炎症和抗菌功能以及与嗜中性粒细胞相互作用能力方面的差异。此外，还讨论了单核细胞亚群向功能极化巨噬细胞的分化。在表型和血液中的分布方面，牛单核细胞亚群与其人类对应物有相似之处。然而，这两个物种的单核细胞亚群之间存在许多功能差异。与它们在人类中的促炎功能相反，牛非经典单核细胞的吞噬作用和活性氧生成能力最低，在炎性小体激活后无法产生促炎细胞因子IL-1β，并且在嗜中性粒细胞早期募集到炎症组织中不起作用。两个物种的经典和中间单核细胞对主要的单核细胞趋化因子（CCL2和CCL5）和嗜中性粒细胞脱颗粒产物（DGP）的反应也不同。同源单核细胞亚群之间的这种差异也延伸到在CCL5等趋化因子和嗜中性粒细胞DGP影响下单核细胞衍生巨噬细胞的发育。虽然后者在人类中诱导M1极化巨噬细胞的分化，但牛单核细胞衍生巨噬细胞呈现混合的M1/M2巨噬细胞表型。尽管只有少数牛临床试验分析了单核细胞组成变化与疾病之间的相关性，但它们表明人类和牛单核细胞亚群之间的功能差异也反映在它们对不同疾病的不同临床相关性上。与人类系统相反，在人类系统中，非经典单核细胞数量增加与多种人类感染性和非感染性疾病广泛相关，而牛中间单核细胞数量增加被认为是产后炎症反应的潜在生物标志物。
