Colorless nitroblue tetrazolium(NBT) is reduced to a water-insoluble formazan which
can easily be recognized as a deep blue deposit in the cytoplasm.
Although the mechanism of reduction of NBT to form formazan in phagocytic
neutrophils is uncertain, Park et al.(1968) reported that the number of neutrophils
reducing NBT dye in vitro was significantly elevated in patients with acute systemic
bacterial infection.
Park(1971) also introduced a simple technique testing intrinsic defect of neutrophils to
phagocytize and kill bacteria, when NBT values are not increased in the presence of
acute bacterial infection, by observing significant rise in NBT positive neutrophila when
Escherichia colo endotoxin is added in vitro.
Walter et al. (1971) found that leukocytes from normal and non-diabetic individuals
had a higher NBT dye-reduction index and a higher phagocytic index than the diabetic
patients. On the other hand, Spirer and Bogair(1973) demonstrated that the NBT
reduction test is normal in well-controlled diabetic patients, and in diabetic acidosis
there is a significant decrease in this function during phagocytosis.
Pujol-Moix(1973) observed that there was no significant difference between the NBT
levels of patients with diabetes alone and normal subjects, and on the other hand,
diabetic patients with associated bacterial infection did not show increased levels of
NBT activity as compared to the corresponding group without infection in spite of the
fact that infections are known to induce increased activity.
The purpose of the present study was to demonstrate difference between NBT leves
of diabetic patients and non-diabetic subjects, and to determine if there is intrinsic
defect of neutrophils in phagocytizing and killing bacteria, by performing stimulated
NBT test.
NBT and stimulated NBT test with E. coli endotoxin were performed on 27 healthy
adults (group Ⅰ), 10 non-diabetic patients with bacterial infection(group Ⅱ), 10 diabetic
patients without bacterial infection(group Ⅲ) and diabetic patients with bacterial
infection(group Ⅳ).
The summary of the results obtained are as following;
1. The total leukocyte count, absolute number of neutrophils and per cent of
neutrophils were significantly increased in group Ⅱ(12,750±360/㎣, 10,392±990/㎣, 81.4±
2.0%) and group IV (12,351±316/㎣, 9,901±685/㎣,80.5±3.8%) in comparison to group Ⅰ
(6,660±331/㎣, 4,030±316/㎣, 57.0±2.2%) and group Ⅲ(6,225±447/㎣, 3,481±367/㎣, 55.0
±2.35) respectively. But there were neither significant difference between group Ⅰ and
group Ⅲ, nor group Ⅱ and group Ⅳ.
2. The absolute numbers of NBT-positive neutrophils in NBT test without stimulation
were significantly increased in group Ⅱ (1,136±301/㎣) and group Ⅳ(494±151/㎣) in
comparison to group Ⅰ(136±25/㎣) and group Ⅲ(99±30/㎣) and respectively. It was
higher with some significance(p<0.1) in group Ⅱ than Ⅳ, but there were no significant
difference between group Ⅰ and group Ⅲ.
3. The per cent of NBT-positive neutrophils in NBT test without stimulation was
significantly higher in group Ⅱ(10.6±2.5%) than group Ⅳ(4.6±1.2%), but there were
neither significant difference between group Ⅰ(3.2±0.5%) and group Ⅱ, group Ⅰ and
group Ⅲ(2.6±0.4%), nor group Ⅲ and group Ⅳ.
4. The absolute numbers of NBT-positive neutrophils in NBT test with stimulation of
E. colo endotoxin were significantly increased in group Ⅱ(3,448±560/㎣) and group Ⅳ
(2,063±476/㎣) in comparison to group Ⅰ(506±72/㎣) and group Ⅲ(361±64/㎣)
respectively. It was higher with some significance(p<0.1) in group Ⅱ than group Ⅳ, but
there was no significant difference between group Ⅰ and group Ⅲ.
5. The per cent of NBT-positive neutrophils in NBT test with stimulation of E. coli
endotoxin was significantly increased in group Ⅱ(32.9±4.2%) and group Ⅳ(20.4±4.2%)
in comparison to group Ⅰ(13.7±1.9%) and group Ⅲ(10.0±1.4%) respectively. But it was
significantly lower in group Ⅳ than group Ⅱ, and there was no significant difference
between group Ⅰ and group Ⅲ.
It might be concluded that while the number and percentage of neutrophils reducing
NBT dye in patients with diabetes mellitus were elevated when bacterial infection was
associated, those were significantly lower in diabetic patients than non-diabetic patients,
and there appears to be some intrinsic defect in neutrophils to phagocytize and kill
bacteria. Also the absolute neutrophil count and stimulated NBT test were more helpful
than per cent of neutrophils and non-stimulated NBT test.
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