DeKuiper Justin L, Coussens Paul M
Department of Animal Science, Michigan State University, East Lansing, MI 48824, USA.
Department of Animal Science, Michigan State University, East Lansing, MI 48824, USA.
Vet Immunol Immunopathol. 2019 Dec;218:109952. doi: 10.1016/j.vetimm.2019.109952. Epub 2019 Sep 26.
Johne's disease (JD) is a chronic inflammatory gastrointestinal disease of ruminants caused by Mycobacterium avium subspecies paratuberculosis (MAP). Control of JD is difficult largely due to insensitive diagnostic tools, a long subclinical stage of infection, and lack of effective vaccines. Correlates of protection are lacking in model systems of JD and the sources of inflammation due to JD are not well characterized. Commonly studied immune responses, such as the Th1/Th2 paradigm, do not adequately explain host responses to MAP. A potential role for non-classical immune responses to MAP, such as that mediated by Th17 cells, has been suggested. Indeed, MAP antigens induce mRNAs encoding the cytokines IL-23 and IL-17a in bovine peripheral blood mononuclear cells (PBMCs). IL-23 and IL-17a production have both been associated with Th17-like immune responses. Th17 cells are also defined by surface expression of the IL-23 receptor (IL-23R). To determine the relative prevalence of potential Th17 cells in PBMCs from MAP test positive and MAP test negative cows, PBMCs were isolated and analyzed by immunostaining and flow cytometry. Fresh PBMCs from MAP test positive cows (n = 12) contained a significantly higher proportion of IL-23R positive cells in populations of CD4+, CD8+, and Yδ + T cells than in cells from MAP test negative cows (n = 12; p < 0.05). Treatment with MAP antigens increased the percentage of all T cell subsets with surface expression of IL-23R when compared to untreated (n = 12; p < 0.05) cells. ELISA results for IL-17a secretion revealed a higher concentration of IL-17a secreted from PBMCs treated with MAP antigen (n = 20) than from PBMCs not treated with MAP antigens (n = 20) (p < 0.001), regardless of the JD test status of source cows. Also, we observed a moderate negative correlation between JD diagnostic scores for JD + cows and plasma IL-17a concentration (n = 42; r = -0.437; p-value < 0.004). Plasma with low and mid JD- scores (n = 31; n = 9; 0.1 ≤ X < 0.3) had significantly more IL-17a when compared to plasma with high JD- scores (n = 10; 0.3 ≤ X < 0.46; p-values < 0.05). Similarly, plasma with low JD + score values (0.55 ≤ X < 1.0; n = 9) had significantly more IL-17a when compared to plasma with high JD + score values (X ≥ 2.0; n = 21; p < 0.05). Overall, plasma from JD + cows (0.55 < X ≤ 2.86; n = 41) had significantly less IL-17a than plasma from JD- cows (0 < X ≤ 0.46; n = 70). Our data suggests that Th17-like cells may indeed play a role in early immune responses to MAP infection and development or control of JD.
副结核（JD）病是由副结核分枝杆菌（MAP）引起的反刍动物慢性炎症性胃肠疾病。JD病的控制难度很大，主要原因是诊断工具不敏感、感染的亚临床阶段较长以及缺乏有效的疫苗。在JD病的模型系统中缺乏保护性关联，并且JD病引起炎症的来源尚未得到很好的表征。常用的免疫反应，如Th1/Th2模式，不能充分解释宿主对MAP的反应。有人提出非经典免疫反应对MAP的潜在作用，如由Th17细胞介导的作用。事实上，MAP抗原可诱导牛外周血单个核细胞（PBMC）中编码细胞因子IL-23和IL-17a的mRNA。IL-23和IL-17a的产生均与Th17样免疫反应有关。Th17细胞也通过IL-23受体（IL-23R）的表面表达来定义。为了确定MAP检测阳性和MAP检测阴性奶牛的PBMC中潜在Th17细胞的相对比例，分离PBMC并通过免疫染色和流式细胞术进行分析。与MAP检测阴性奶牛（n = 12）的细胞相比，MAP检测阳性奶牛（n = 12）的新鲜PBMC在CD4 +、CD8 +和Yδ + T细胞群体中IL-23R阳性细胞的比例显著更高（p < 0.05）。与未处理的细胞（n = 12；p < 0.05）相比，用MAP抗原处理可增加所有具有IL-23R表面表达的T细胞亚群的百分比。IL-17a分泌的ELISA结果显示，无论来源奶牛的JD检测状态如何，用MAP抗原处理的PBMC（n = 20）分泌的IL-17a浓度高于未用MAP抗原处理的PBMC（n = 20）（p < 0.001）。此外，我们观察到JD +奶牛的JD诊断评分与血浆IL-17a浓度之间存在中度负相关（n = 42；r = -0.437；p值< 0.004）。与高JD -评分（n = 10；0.3≤X < 0.46；p值< 0.05）的血浆相比，低和中JD -评分（n = 31；n = 9；0.1≤X < 0.3）的血浆中IL-17a显著更多。同样，与高JD +评分值（X≥2.0；n = 21；p < 0.05）的血浆相比，低JD +评分值（0.55≤X < 1.0；n = 9）的血浆中IL-17a显著更多。总体而言，JD +奶牛（0.55 < X≤2.86；n = 41）的血浆中IL-1
