Analysis of regulatory T cell associated forkhead box P3 expression in the lungs of patients with sarcoidosis

In pulmonary sarcoidosis, the typical T helper 1-mediated immune response in the lungs has been proposed to be co-ordinated by regulatory T cells; however, their exact role needs to be clarified. We used real-time polymerase chain reaction to study genes involved in regulatory T cell functions in CD4(+) T cells isolated from bronchoalveolar lavage fluid (BALF) of patients (n = 24) and healthy subjects (n = 7). The genes included the transcription factor forkhead box P3 (FoxP3), interleukin (IL)-10, transforming growth factor-beta 1 and chemokine receptor 2 (CCR2). The same genes were also studied in isolated BALF CD4(+) T cell receptor AV2S3(+) and AV2S3(-) T cells of patients with lung-restricted AV2S3 T cell expansions (n = 12). Intracellular staining of the FoxP3 protein was performed additionally in 14 patients and nine healthy subjects. mRNA expression of FoxP3, CCR2 and IL-10 was decreased significantly in BALF CD4(+) T cells of patients. Flow cytometric analysis of CD4(+) T cells also demonstrated a decreased frequency of FoxP3(+) cells in the BALF and blood of sarcoidosis patients as well as a reduced intensity (mean fluorescence intensity) of FoxP3 expression in BALF FoxP3(+) cells of patients. BALF CD4(+)AV2S3(+) T cells expressed significantly lower levels of FoxP3 and CCR2 mRNA versus BALF CD4(+)AV2S3(-) T cells. The main conclusion of our study is that there is a reduced expression of regulatory T cell associated genes in BALF CD4(+) T cells in sarcoidosis. In addition, our data suggest an effector function of AV2S3(+) lung-accumulated T cells in sarcoidosis.