Skewing of the CD8+ T-cell repertoire in the lungs of patients with systemic sclerosis

Abstract

Pulmonary parenchymal involvement in SSc is characterized by alveolitis and interstitial fibrosis, with an increased number of CD8+ T cells in BAL fluids. This study analyzed the diversity of the alphabeta T-cell repertoire in peripheral blood and BAL fluids from seven SSc patients, looking for evidence of antigen-driven selection of T cells in the lungs. A reverse transcriptase-polymerase chain reaction technique was used to amplify rearranged TCR transcripts from unfractionated, CD4+, and CD8+ T cells. Nearly all AV and BV gene families were expressed in SSc patients and most had similar levels of expression in blood and BAL samples. Next, the diversity of TCR junctional region lengths was assessed, using sequencing gel electrophoresis. Many V gene families had a Gaussian distribution of their junctional region lengths. However, some V gene families had an abnormal pattern of junctional lengths, with skewing away from a Gaussian distribution, including predominance of one or two lengths. This suggests selected expansion of T cells expressing those V genes. Alterations in TCR junctional region lengths were most prominent in bronchoalveolar CD8+ T cells, with similar patterns of skewing in several patients and in one patient over time. Sequence analysis of AV14 and BV17 junctional regions confirmed the oligoclonal character of expansion of bronchoalveolar CD8+ T cells.