When the inflammatory phase of sarcoidosis has resolved, complaints of chronic fatigue frequently persist. Low-grade residual inflammatory activity may play a role in maintaining chronic fatigue. The aim of this study was to compare in vitro cytokine/chemokine production and plasma cytokine/chemokine levels between chronically fatigued and non-fatigued patients with sarcoidosis in clinical remission. Patients with sarcoidosis in clinical remission were assigned to a non-fatigued group (n=38) or a fatigued group (n=34) based on the standardized cut-off of the fatigue questionnaire Checklist Individual Strength. Cytokines/chemokines in plasma and in supernatants of whole blood cultures stimulated with either a T cell mitogen or lipopolysaccharide were quantified by multiplex analysis. Associations of cytokine/chemokine profiles with chronic fatigue were analyzed by multivariate analysis of variance and principal component analysis followed by logistic regression. Principal component analysis of T cell mitogen-induced cytokine/chemokine production identified three components that explained 76% of the variance in the cytokine/chemokine data. Logistic regression revealed that the 'Th2 cytokine'-component which mainly consists of interleukin (IL)-4, IL-5 and IL-10 was significantly and negatively associated with chronic fatigue. In addition, multivariate analysis revealed higher levels of LPS-induced IL-8 and lower levels of plasma monocyte chemoattractant protein (MCP)-1 in the fatigued group compared to the non-fatigued group. In chronically fatigued sarcoidosis patients in clinical remission, we found a cytokine/chemokine profile which is suggestive for a less competent Th2 counterbalancing capacity, that may contribute to the persistence of chronic fatigue.
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