Glycophorin A (GPA) variant erythrocytes in 131I-Treated patients

GPA is the determinant molecule of the MN blood group system. It occurs in two common forms, products of the GPAM and GPAN alleles. In individuals of the blood group MN rare red blood cell variants can be detected that express only one of the GPAs as a result of in vivo allele loss at the GPA gene in erythroid precursor cells in the bone marrow. Irradiation of the bone marrow is followed by a permanent increase of the frequency of GPA variant erythrocytes. The frequency of GPAN/0 (VF[N0]) and GPAN/N (VF[NN]) variant cells was measured in 34 patients after radioiodine treatment for thyroid cancer. Twenty-one of them children from the Byelorussian Republic. They came from areas heavily contaminated after the Chernobyl nuclear power plant accident. The red bone marrow dose was calculated from the total 131I activity given according to ICRP 53 (1988). Dose varied from 83 to 1969 mGy. GPA variant cells were determined by the MACS-BR6 assay. A dose as low as 0.1 to 0.3 Gy resulted in a significant increase of VF [NO] and VF[N0+NN]. A significant increase of VF[NN] could only be found at a dose of about 1 Gy. The trend of the dose dependent increase of VF was estimated by assuming a linear model. A linear dose relationship of VF[N0] and VF[N0+NN] is significant. In 9 children VF could be measured before and about one year after radioiodine treatment. In these patients a red bone marrow dose as low as 0.1 to 0.2 Gy resulted in a significant increase in VF[N0] and VF[N0+NN]. (authors)