Immune responses in defined subgroups of patients with pulmonary sarcoidosis

Abstract: This thesis focuses on inflammatory responses in the airways of sarcoidosis patients. Sarcoidosis is a T helper 1-mediated inflammatory disease with unknown aetiology. HLA-DRB1'0301pos sarcoidosis patients often present with an acute form of disease, i.e. Löfgren s syndrome, usually with a very good prognosis. These patients also have expansions of CD4+ T cells expressing the T cell receptor AV2S3 gene segment in their lungs. The overall aim of these studies was to investigate the inflammatory and immune regulatory responses in sarcoidosis and in specific subgroups of patients, compared to healthy controls. The cytokine profile in bronchoalveolar lavage fluid (BALF) of patients revealed that the levels of mRNA and protein expression of pro-inflammatory and Th1 associated cytokines were in general increased in sarcoidosis patients compared to healthy individuals. In particular, HLA-DRB1'0301neg patients expressed significantly increased levels of pro-inflammatory and Th1 associated cytokines in their lungs as compared to HLA-DRB1'0301pos patients and controls. A tendency to a higher expression of TGF- beta1 was seen in DRB1'0301pos patients. The study of BALF CD4+ T cells in patients revealed decreased mRNA levels of the T regulatory cell-specific transcription factor, FOXP3, and of regulatory associated genes IL-10 and CCR2. Furthermore, at the protein level reduced frequencies of FOXP3- expressing BALF and blood CD4+ T cells were observed in patients. The mean fluorescence intensity of FOXP3 expression in BALF FOXP3+ CD4+ cells of patients was also reduced. AV2S3+ CD4+ T cells expressed significantly reduced levels of FOXP3 and CCR2 compared to the other BALF CD4+ T cells. We did not find any differences in the expression of CCR2, FOXP3, IL-10 and TGF-beta1 between patient subgroups. Sarcoidosis patients expressed decreased levels of T-cell immunoglobulin and mucin domain (TIM)-3 mRNA in their BALF CD4+ T cells, as compared to healthy subjects, while IL-2 expression was increased in patients. TIM molecules have been suggested to be important regulators of immune functions. In addition, our data revealed an increased mRNA level of IFN-gamma in non-Löfgren s patients as compared to Löfgren s patients, while the mRNA level of TIM-1 was decreased. Analyzing alveolar macrophages, we detected a significantly lower expression of TLR2 in patients, in particular patients with Löfgren s syndrome. We also observed that the gene expression of fibrosis-associated CCL18 was higher in patients compared to controls. There was a tendency to higher IL-23 levels in cultured BALF cells of patients, but upon LPS-stimulation it was markedly more upregulated in healthy controls. In conclusion, the reduced immune regulatory response in the lungs of sarcoidosis patients may result in an uncontrolled inflammation particularly in non-Löfgren s patients, contributing to the pathogenesis of this disease. AV2S3+ T cells in the lungs of Löfgren s patients seem to have an effector function and may contribute to the eradication of a postulated sarcoidosis antigen.