Yellow nitroblue tetrazolium

The ability of a test compound to induce differentiation of HL-60 cells (derived from a patient with acute promyelocytic leukaemia) is also an important assay of retinoid activity [91-93]. HL-60 cells do not produce superoxide anions upon stimulation by agents like TPA. Differentiated HL-60 cells, however, do produce these anions upon similar stimulation. The presence of these anions can be monitored because of their ability to reduce the yellow nitroblue tetrazolium (NBT) to the water insoluble blue-black formazan. Determination of the concentration (ED50) which results in differentiation of 50% of the cells is the measure of the anti-APL activity of the retinoid. Morphological maturation of the cells can also be checked. 

The wide range of chromogenic-substrate systems available allows one to obtain excellent color contrast for double/multiple antigen detection. Chromo-genie reactions resulting in black (IGSS), yellow-brown (IPO/DAB), red-brown (IPO/AEC), blue (lAP/Fast Blue, or 5-bromo-4-chloro-3-indolyl phosphate/ nitroblue tetrazolium [BCIP-NBT]), and purple (lAP/Fast Red or New Fuchsin) can be used in different combinations (see Chapter 23). For development of these products, the following protocols are provided (see Note 16). 

Principle The respiratory burst of phagocytic cells can be assessed by incubating a suspension of the cells in an isotonic solution of the yellow oxidised nitroblue tetrazolium (NBT) dye. During this process, the soluble dye interacts with the cytoplasmic components associating with the oxidant species generated. Although the NBT test is not a specific marker for superoxide production, NBT reduction by activat-... 

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