Candidacidal activity of Crohn's disease neutrophils. The ability of normal and Crohn's disease neutrophils to kill Candida albicans has been studied using neutrophils isolated from peripheral blood and suspended in phosphate buffered saline at 5 x 10(6) cells per ml. C albicans was grown to a stationary phase in broth culture and suspended in phosphate buffered saline at 10(7) organisms/ml. Neutrophils and Candida were then incubated together at 37 degrees C in a shaking water bath in the presence of fresh serum. At 30 and 60 minutes samples were withdrawn, neutrophils lysed, and Candida survival assessed by colony counting. Results were compared with control suspensions of Candida incubated with serum alone. After 30 and 60 minutes in the presence of autologous serum normal neutrophils had killed significantly more Candida than Crohn's disease neutrophils (mean (SD) 61.0 (16.7)% v 40.5 (16.2)% at 30 minutes, p less than 0.0001; 83.2 (7)% v 70.8) 16)% at 60 minutes, p less than 0.005). The results did not alter significantly when normal neutrophils were incubated with Candida in the presence of Crohn's disease serum instead of normal serum. When Crohn's disease neutrophils were incubated with Candida in the presence of normal serum instead of autologous serum there was some improvement in candidacidal ability at 30 minutes (48.9 (20.6)% v 40.5 (16.2)%, p less than 0.03) but not at 60 minutes. Phagocytosis, measured using a radiometric assay, was normal. Neutrophils from patients with Crohn's disease have an impaired ability to kill this granuloma provoking organism. It is not due to serum inhibitors or defective phagocytosis. 