We analyzed the T cell receptor (TCR) repertoire of bronchoalveolar lavage fluid (BALF) lymphocytes from polymyositis (PM) and dermatomyositis (DM) patients with interstitial pneumonitis (IP) to elucidate the pathogenic mechanisms of IP in these disorders. Samples from 2 PM patients, 1 DM patient and 3 healthy controls were used. RNA was isolated from BALF, cDNAs were synthesized, and family PCR and Southern blot analysis were performed by primers specific for TCR BV1-25 and TCR BC to determine TCR repertoire. We examined single-strand conformation polymorphism (SSCP) to evaluate T cell clonality. The CDR3 region of TCR BV genes in BALF T cells were determined by DNA sequencer. Our examination showed that TCR repertoire of T cells in BALF was heterogeneous both in patients with PM/DM and control subjects. SSCP analysis demonstrated an increased number of accumulated T cell clones in BALF of three PM/DM patients, but not in the healthy subjects and the junctional sequence analysis showed the presence of conserved amino acid motifs (RGS, GLA, LQG, SGG, DRG, GTS, TSGR, GGS, GQA, GAG, GTG) in the TCR-CDR3 region of BALF lymphocytes from PM/DM patients, which were not detected in the control. Our findings suggest that T cells in BALF may recognize the restricted antigen and accumulate via antigen-driven stimulation, suggesting that T cells may play a crucial role in the development of IP in patients with PM/DM.

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