Schiwietz J, Lorenz R, Scheubeck M, Börner W, Hempel K
Institute of Medical Radiation and Cell Research, University of Würzburg, Germany.
Int J Radiat Biol. 1996 Aug;70(2):131-43. doi: 10.1080/095530096145120.
Red blood cells from individuals with the blood group MN express each form of the allelic GPA protein (GPAM and GPAN) on their cell surface. Variant cells have lost one form of the protein. Their frequency is about 10(-5) in blood from unexposed persons. The BR6 assay is currently the most widely used assay to determine variant frequency (VF) by immunolabelling and flow cytometry. The precision of the BR6 assay is mainly limited by the Poisson error because only small numbers of variant cells are detected in each assay. The BR6 assay has been improved by magnetic cell separation (MACS) of variant erythrocytes prior to their determination by this assay. This new version of the assay is named 'MACS-BR6'. It allows enumeration of variant cells from 2 x 10(8) or more blood cells instead of 5 x 10(6) in the BR6 assay with a precision which is about 5 times higher than that of the BR6 assay. The MACS-BR6 assay was used to determine the VF of GPAN/0 and GPAN/N variant cells in 12 healthy adults and 11 patients treated with radioiodine for thyroid cancer 2 to 16 years before. The average red bone marrow dose was 347 mGy. In healthy adults the mean VF of GPAN/0 and GPAN/N variant cells was 16.1 x 10(6) and 5.3 x 10(-6) respectively. In patients the corresponding mean VF was 25.4 x 10(6) and 11.9 x 10(-6), respectively. The patients GPAN/0 VF was significantly higher than that of controls. In patients VF increases linearly with the dose. The linear regression parameters of VF were 16.6 x 10(-6) (intercept), 23.7 x 10(-6) GY-1 (slope) and 6.3 x 10(-6) (intercept), 12.9 x 10(-6) Gy-1 (slope) for GPAN/0 and GPAN/N variant cells, respectively.
MN血型个体的红细胞在其细胞表面表达等位基因GPA蛋白的每种形式（GPAM和GPAN）。变异细胞失去了其中一种蛋白形式。在未接触者的血液中，它们的频率约为10^(-5)。BR6检测是目前通过免疫标记和流式细胞术测定变异频率（VF）最广泛使用的检测方法。BR6检测的精度主要受泊松误差限制，因为每次检测中只能检测到少量变异细胞。在通过该检测法测定变异红细胞之前，通过磁性细胞分离（MACS）对BR6检测进行了改进。该检测法的新版本名为“MACS-BR6”。它能够从2×10^8个或更多血细胞中计数变异细胞，而不是BR6检测中的5×10^6个，其精度比BR6检测高约5倍。MACS-BR6检测法用于测定12名健康成年人以及11名在2至16年前接受过放射性碘治疗甲状腺癌的患者中GPAN/0和GPAN/N变异细胞的VF。平均红骨髓剂量为347毫戈瑞。在健康成年人中，GPAN/0和GPAN/N变异细胞的平均VF分别为16.1×10^(-6)和5.3×10^(-6)。在患者中，相应的平均VF分别为25.4×10^(-6)和11.9×10^(-6)。患者的GPAN/0 VF显著高于对照组。在患者中，VF随剂量呈线性增加。GPAN/0和GPAN/N变异细胞的VF线性回归参数分别为16.6×10^(-6)（截距）、23.7×10^(-6) Gy^(-1)（斜率）以及6.3×10^(-6)（截距）、12.9×10^(-6) Gy^(-1)（斜率）。
