Nitroblue tetrazolium (NBT) activity in human leucocytes after freezing

Human peripheral blood leucocytes (neutrophil-rich) were collected either with heparin or acid citrate dextrose, frozen with dimethyl sulphoxide at a controlled rate, stored in liquid nitrogen at--196 degrees C and reconstituted with a solution containing dextran. After reconstitution, 20.2% of cells (in absolute numbers 1 in 5 fresh cells) showed a strongly positive nitroblue tetrazolium (NBT) reaction. The quantitative NBT test confirmed the synthesis of formazan/10(6) reconstituted neutrophilsa s15% of the fresh capacity. A slow titration reconstitution method for cells did not improve the functional capacity of thawed leucocytes as judged by the NBT test. When comparing anticoagulants, heparin increased the post-reconstitution cell yields after freezing and increased the absolute number of reconstituted cells capable of developing a positive NBT reaction.