Down regulation in hypersensitivity pneumonitis.

Levels of soluble interleukin-2 receptor (sol-IL-2R) in the bronchoalveolar lavage fluid (BALF) of pigeon breeders with hypersensitivity pneumonitis were compared with BALF levels in asymptomatic pigeon breeders who had been exposed to pigeon allergens for an equivalent length of time. No mean difference in sol-IL-2R levels was detected when these levels were expressed per milliliter BALF, epithelial lining fluid, or per T-lymphocyte. In sarcoidosis, the availability of sol-IL-2R per T cell was significantly higher for the group with inactive sarcoidosis compared with the group with active sarcoidosis. The results do not support the hypothesis that down regulation, in subjects exposed to allergens causing hypersensitivity pneumonitis, is a function of cell-free sol-IL-2R levels in BALF. In the dynamic situation, however, the hypothesis appears tenable.