Institute of Veterinary Bacteriology, Vetsuisse Faculty, University of Bern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Switzerland.
Institute of Virology and Immunology, 3147 Mittelhäusern, Switzerland; Graduate School for Cellular and Biomedical Sciences, University of Bern, Switzerland.
Vet Microbiol. 2020 Jan;240:108541. doi: 10.1016/j.vetmic.2019.108541. Epub 2019 Nov 29.
Mycoplasma (M.) hyopneumoniae is the etiological agent of enzootic pneumonia in pigs and is closely related to M. hyorhinis, which can be isolated from the healthy mucosal surfaces of the upper respiratory tract. In rare cases it can also cause arthritis and polyserositis. Since the innate immune system is an important first line of defense and promotes adaptive immune responses, we characterized the innate immune response of various antigen presenting cells (APCs) to M. hyopneumoniae and M. hyorhinis, which differ in their pathogenicity in vivo. Porcine peripheral blood mononuclear cells were infected with different multiplicities of infection (MOI) of live and inactivated porcine mycoplasmas. Both Mycoplasma species induced strong tumour necrosis factor (TNF) responses in monocytes, with a stronger activation by M. hyorhinis. This higher stimulatory activity was also confirmed for CD40 upregulation. Conventional and plasmacytoid dendritic cells (cDC and pDC, respectively) did not or poorly respond to mycoplasmas in terms of TNF expression but more efficiently in terms of CD40 upregulation. Again, these responses were generally stronger with M. hyorhinis than with M. hyopneumoniae. Both Mycoplasma species also activated B cells in terms of CD25 upregulation, proliferation, and IgM secretion. Interestingly, while the induction of CD25 and in particular proliferation was higher with M. hyorhinis, the IgM secretion did not differ between the two species with the exception of the highest dose of M. hyopneumoniae,which appeared to suppress IgM responses. Taken together, our results provide a comparative analysis of innate immune response with different porcine APCs and demonstrate Mycoplasma species-dependent differences, which could relate to their different pathogenicity in vivo.
猪肺炎支原体（M. hyopneumoniae）是猪地方性肺炎的病原体，与可从猪上呼吸道健康黏膜表面分离的 M. hyorhinis 密切相关。在极少数情况下，它也会引起关节炎和多发性浆膜炎。由于先天免疫系统是重要的第一道防线，并促进适应性免疫反应，我们对不同的抗原呈递细胞（APCs）对 M. hyopneumoniae 和 M. hyorhinis 的先天免疫反应进行了特征描述，这两种支原体在体内的致病性不同。猪外周血单核细胞用不同的感染复数（MOI）感染活的和灭活的猪支原体。两种支原体都能强烈诱导单核细胞产生肿瘤坏死因子（TNF），而 M. hyorhinis 的激活作用更强。CD40 上调也证实了这种更高的刺激活性。在 TNF 表达方面，常规和浆细胞样树突状细胞（cDC 和 pDC）对支原体没有反应或反应较差，但在 CD40 上调方面反应更有效。同样，这些反应通常随着 M. hyorhinis 的增强而增强，而不是 M. hyopneumoniae。两种支原体都能以上调 CD25 的方式激活 B 细胞、增殖和 IgM 分泌。有趣的是，虽然 M. hyorhinis 诱导 CD25 的表达，特别是增殖的能力更高，但除了最高剂量的 M. hyopneumoniae 似乎抑制 IgM 反应外，两种支原体之间的 IgM 分泌没有差异。综上所述，我们的结果提供了不同猪 APCs 的先天免疫反应的比较分析，并证明了支原体物种依赖性的差异，这可能与它们在体内的不同致病性有关。
