Stimulation of BAL cells (a) and PBMCs (b) from the CBD patients. Proliferation of the cells in medium alone and after the addition of 1 × 10^–5 M BeSO₄ is shown. Proliferation assays were performed with BAL cells from 8 of the 12 CBD patients and with PBMCs from 9 of the 12 patients. The stimulation index (SI) for each proliferative response is shown over the corresponding bar, and an SI indicative of a positive response is currently defined as ≥ 2.5. The data are expressed as the mean cpm ± SEM.