Crystal-phagocyte interaction in calcinosis interstitialis

Based on recent findings indicating the stimulation of the respiratory burst in human neutrophils by crystal phagocytosis, ectopic calcified nodules of a patient with calcinosis interstitialis were exposed to autologous granulocytes and monocytes in vitro. The activity of the respiratory burst was determined by luminol-enhanced chemiluminescence. Controls included amorphous monosodium urate, microcrystalline monosodium urate, hydroxyapatite, and zymosan. Microcrystalline monosodium urate elicited a marked stimulation of both granulocytes and monocytes as did hydroxyapatite in granulocytes. Hydroxyapatite caused no stimulation of monocytes, possibly reflecting selective functional modulation. On the other hand, amorphous monosodium urate failed to induce a respiratory burst with granulocytes or monocytes. Likewise, the contents of the nodule evoked only marginal stimulatory activity on the phagocytes. Stimulation by zymosan was normal with both cell types. The finding that material of the excised nodule failed to induce a respiratory burst in phagocytes may explain the lack of inflammatory reaction in vitro around the nodules on histologic examination, particularly since products of stimulated phagocytes have been described as causing tissue destruction.