Phagocytosis measured as inhibition of uridine uptake by Candida albicans

Inhibition of 3H-uridine incorporation into Candida albicans can be used as a sensitive index of phagocytic function because: 1) there is a linear correlation between uridine incorporation and yeast number; 2) phagocytic cells do not incorporate significant amounts of uridine in short term cultures; and 3) C. albicans replicating inside phagocytic cells does not take up uridine from culture medium. Appropriate conditions for measuring phagocytic capacity of human polymorphonuclear cells (PMN's) were 5 x 10(5) C. albicans and 5 x 10(4) PMNs in 0.5 ml of medium containing 2.5% AB serum. This mixture was incubated for 30 min at 37 degrees C. Aliquots were then transferred into microtiter wells and incubated for a further 60 min in the presence of 3H-uridine. Under these conditions PMN leucocytes from 25 healthy individuals caused suppression of uridine incorporation ranging from 33 to 75% (50 +/- 12).