Abstract
Hypersensitivity pneumonitis (HP) is characterized by a lung lymphocytosis. Most individuals exposed to HP antigens remain asymptomatic. The mechanisms involved in the impaired immune tolerance leading to HP are unclear. Normally, T regulatory cells (Treg) control the immune response. Could Treg suppressive function deficiency explain the uncontrolled inflammation in HP?
Bronchoalveolar lavage (BAL) and blood samples were obtained from normal subjects, asymptomatic individuals, and HP patients. BAL and blood Treg were isolated. The ability of Treg to suppress T cell proliferation and the role of IL-17 was verified.
BAL and blood Treg cells from normal subjects suppressed the proliferative response of activated T cells by 47.1% and 42% respectively. BAL and blood Treg cells from asymptomatic subjects had a slightly decreased activity and suppressed proliferation by 29.4% and 31.8% respectively. BAL and blood Treg from HP patients were totally non functional and unable to suppress proliferation.
Low levels of IL-17 were detected in sera and BAL from both normal and asymptomatic individuals whereas measurable levels were found in patients.
Treg may be involved in the antigen tolerance in asymptomatic subjects. A defective Treg function, potentially because of increased IL-17 production, could account for the exacerbated immune response characteristic of HP.
- ERS