A microassay for nitroblue tetrazolium reduction by human neutrophils

By adapting the nitroblue tetrazolium reduction test (NBT test) of neutrophil function to microtiter plates with correspondingly small incubation and dye extraction volumes, it has been possible to develop a microassay with the following advantages: 1. The cell number required for single standard assay has been reduced five- to tenfold to 1 X 105 PMN. 2. If little blood or few cells are available, this number can be further reduced to 1-5 X 104. 3. The test is rapid (less than 6 hours overall) and highly reproducible. 4. A single technician can process at least six plates = 576 single assays at a time. 5. Due to the small incubation volume, test substances can be saved. NBT reduction in this test is a function of both cell number and concentration of the stimulus (here: zymosan). Addition of serum, Mg+/-+/-, or EGTA/Mg enhances the response to zymosan while Ca+/- +/- at greater than or equal to 2 mM is inhibitory.