Patients with idiopathic endplate inflammation displayed aberrant Th17 responses resulting in proinflammatory monocyte activation

Abstract

Endplate inflammation remains a difficult task to diagnose and treat, partly due to the absence of in-depth understanding of the cellular and molecular factors driving this condition. In the current study, we investigated the circulating immune cells in patients with idiopathic endplate inflammation. Compared to healthy controls, the patients with endplate inflammation presented a significant upregulation of Th17 cells, characterized by higher frequencies of circulating IL-17+CD4+ T cells examined directly ex vivo and after PMA and ionomycin (PMA/I) stimulation. The frequency of Th17 cells in patients was not correlated with patient age, sex, or smoking status, but was significantly correlated with patient BMI. The total CD4+ T cells from patients with end plate inflammation also presented significantly higher levels of IL-17 secretion directly ex vivo and after PMA/I stimulation. The IL-17 secretion was primarily mediated by CCR4+CCR6+ CD4+ T cells, followed by CCR4-CCR6+ CD4+ T cells and was nearly absent in CCR4-CCR6- CD4+ T cells. Monocytes incubated with CCR4+CCR6+ CD4+ T cells presented significantly higher MHC class II expression, as well as higher CD80 and CD86 expression. The secretion of IL-6 and TNF was significantly higher in cell cultures containing CCR4+CCR6+ CD4+ T cells than in cell cultures containing CCR4-CCR6- CD4+ T cells. These effects were reduced when the IL-17A cytokine was neutralized. Together, we identified a systemic upregulation of Th17 responses that could contribute to proinflammatory monocyte activation in patients with endplate inflammation.