NBT and stimulated NBT test in patients with diabetes mellitus
당뇨병환자에서 감염이 자주 동반될 수 있음은 이미 잘 알려져 있으며, 그 기전에 대하여서는 아직 명확히 알려져 있지는 않으나 백혈구의 기능, 즉 탐식력 내지는 세포내 살균작용에 이상이 있을 것으로 추정되어 이에 대한 연구가 많았다.
정상이 27예와 세균감염증만 동반한 비 당뇨병환자 10예를 대조군으로 하고 세균감염증이 없는 당뇨병환자 10예 및 감염증을 동반한 당뇨병환자 10예를 대상으로 NBT 및 대장균내독소를 이용한 stimulated NBT검사를 시행하였다.
대장균 내 독소로 자극하지 않은 NBT검사시, NBT양성 중성구의 절대 수는 대조군과 당뇨병환자군 각각에서 감염이 있을 때 의의 있게 증가하나 그 백분율의 증가는 통계적 의의가 없었다.
한편 감염이 없는 경우, NBT양성 중성구의 절대 수 및 백분율은 당뇨병환자군에서 정상 대조군 보다 야간 낮은 경향을 보이면서도 통계적 의의는 없었지만, 감염이 있을 때는 당뇨병 환자군에서 대조군보다 의의 있게 낮았다.
대장균 내 독소로 자극한 sNBT양성 중성구의 수 및 그 백분율은, 대조군과 당뇨병환자군 각각에서, 감염이 있을 때 의의 있는 증가를 보였으며, 감염이 없는 당뇨병환자에서는 감염이 없는 대조군 보다 약간 낮은 경향이나 의의가 없었음에 반하여, 감염이 있을 경
우 당뇨병환자에서 대조군 보다 의의 있게 낮은 수치를 보였다
따라서 감염이 당뇨병환자에서 자주 동반되는 원인의 하나로서 백혈구의 기능, 즉 탐식력 내지는 세포 내 살균력의 이상이 관련되는 것으로 추정된다.
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 neutrophils when Escherichia coli 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 had, Spirer an Bogair(1973) demonstrated that the NBT reduction test is normal in well-controlled diabetic patients, and in
diabetic acidosis there is a significant decrease int his 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 levels 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/mm**3, 10.392±990/mm**3, 81.4±2.0%) and group Ⅳ (12.351±682/mm**3, 9.901±685/mm**3, 80.5±3.8%) in comparison to group Ⅰ (6.660±331/mm**3, 4.030±316/mm**3,
57.0±2.2%) and group Ⅲ (6.225±447/mm**3, 3.481±367/mm**3, 55.0±2.3%), 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/mm**3) and group Ⅳ(494±151/mm**3) in comparison to group Ⅰ (136±25/mm**3) and group Ⅲ(99±30/mm**3), respectively. It was higher with some significance (p<0.1) in group Ⅱ than group 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. coli endotoxin were significantly increased in group Ⅱ(3.448±560/mm**3) and group Ⅳ (2.063±476/mm**3), in comparison to group Ⅰ (506±72/mm**3) and
group Ⅲ (361±64/mm**3), 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.M 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 percent of neutrophils and non-stimulated NBT test.