[Nitroblue-tetrazolium test in isolated human monocytes]

Depending upon the NBT charge 50 to 80% of isolated non stimulated human monocytes reduce NBT ro morphologically demonstrable Formazan. Similar to neutrophils two different patterns of reaction are exhibited: discrete load with finely distributed Formazan granula surrounding the nucleus; massive reaction with large distributed Formazan granula surrounding the nucleus; massive reaction with large Formazan deposits throughout the cytoplasma. In a low percentage morphologically desintegrated, massive loaden cells appear. After an additional incubation in medium without NBT the number of these necrotic cells increases. The phagocytosis of IgG-coated red cells is impaired after incubation of the monocytes in NBT. In the presence of an alkylating agent not only the NBT-reaction is inhibited; the number of necrotic cells is also diminished. Apparently the Formazan is cytotoxic. The significance of these results in particular in cases of enhanced NBT reduction is discussed. Compared with the findings of other authors concerning the neutrophils the monocytes possess a markedly stronger NBT reducing activity. Considering the lower bactericidal capacity of the monocytes NBT reduction does not in every case parallel bactericidal activity.