Figure 2.

Human macrophages express the CYP27B1-hydroxylase. Macrophages harvested from the alveolar or pleural space of patients with active granuloma-forming disease of the lung (left panel; e.g., sarcoidosis and tuberculosis) and plated in monolayer at high density (right panel) synthesize and secrete 1,25-dihydroxyvitamin D3 (1,25D3) when incubated with physiologically relevant concentrations of substrate 25-hydroxyvitamin D3 (25D3). The specific activity of the 1-hydoxylation reaction is significantly increased if monolayer cultures of macrophages are preconditioned in medium containing rhIFN-γ or patient-derived pulmonary alveolar fluid enriched in IFN-γ.