Increased T-cell receptor V beta 8+T cells in bronchoalveolar lavage fluidof subjects with poorly controlled asthma: A potential role for microbial superantigens

Background: T cells are thought to play an important role in the pathogenes is of chronic asthma, The immunologic triggers that contribute to poorly co ntrolled asthma are unknown but may include infectious agents. Superantigen s (SAgs), which stimulate T cells expressing selected T-cell receptor (TCR) beta-chain variable (V beta) regions, are known to be an important mechani sm by which microbes can contribute to T-cell activation and disease pathog enesis. Objective: We sought to determine the potential role of SAgs in T-cell acti vation of patients with poorly controlled asthma, Methods: We studied the TCR-V beta repertoire of bronchoalveolar lavage (BA L) cells and PBMCs from 9 subjects with poorly controlled asthma (FEV1 <75% ), 7 subjects with well-controlled asthma (FEV1>80%), and 8 normal control subjects with the use of anti-TCR-V beta-specific mAbs and flow cytometry, Results: Subjects with poorly controlled asthma had a significantly higher expression of V beta 8(+) T cells in BAL fluid than subjects with well-cont rolled asthma and normal control subjects (P <.01) and autologous PBMCs (P <.05), Increased V beta 8(+) BAL T cells were present in CD4(+) (P <.01) an d CD8(+) (P <.05) subsets, suggesting activation by SAgs, Conclusion: These results indicate that SAgs are a potential trigger of T-c ell activation in poorly controlled asthma.