An unusual variant glycophorin expressing protease‐resistant M antigen encoded by the GYPB‐E(2‐4)‐B hybrid gene

GP.MOT: A novel glycophorin variant identified in a Japanese blood donor

BACKGROUND

In this study, we identified a novel glycophorin variant (GP.MOT) in a Mi^a -positive Japanese blood donor. The proband with this glycophorin variant was discovered by antigen screening of samples from 475,493 Japanese blood donors using monoclonal anti-Mi^a .

STUDY DESIGN AND METHODS

Standard serological techniques and flow cytometry were performed. GP.MOT RBCs were examined by immunoblotting using anti-GPA, anti-MUT or anti-Mur. Genome DNA was extracted from whole blood, and the GYPA/GYPB was analyzed by polymerase chain reactions and Sanger sequencing.

RESULTS

The MNS blood group of the proband was M + N + ^w S-s + with the presence of other low-frequency antigens including Mi^a , Mur, MUT, and KIPP. A 43-kDa molecule, which is almost equivalent in size to glycophorin A (GPA), was identified by immunoblotting using monoclonal anti-MUT and anti-Mur. Sanger sequencing clearly indicated that the proband had two different GYPA*M alleles at SNP rs62334651 (GYPA*M232 + 55A and GYPA*M232 + 55G), as well as a GYP(B-A) hybrid allele (GYP*MOT) with breakpoints located on pseudoexon 3 of GYPB from c.210 to c.219.

DISCUSSION

We identified a hybrid glycophorin GP.MOT with the deduced unique amino acid sequence GPB (20-45)-GPΨB (46-70)-GPA (71-149), which has not been previously reported.

Frequencies of glycophorin variants and alloantibodies against Hil and MINY antigens in Japanese

BACKGROUND AND OBJECTIVES

Antigens of the MNS blood group system are expressed on the red blood cell (RBC) membrane on glycophorin A (GPA) and glycophorin B (GPB) or on hybrid molecules of GPA and GPB. This study investigated the distribution of glycophorin variants and alloantibodies against Hil and MINY among Japanese individuals.

METHODS

Mi(a+) or Hil+ RBCs were screened using an automated blood grouping machine (PK7300) with monoclonal anti-Mi^a or polyclonal anti-Hil. Glycophorin variants were defined by serology with monoclonal antibodies against Mi^a , Vw, MUT and Mur, and polyclonal antibodies against Hil, MINY and Hop + Nob (KIPP). The glycophorin variants were further confirmed by immunoblotting and Sanger sequencing. Alloanti-Hil and alloanti-MINY in the plasma were screened using GP.Hil RBCs in an antiglobulin test. The specificity of anti-Hil or anti-MINY was assessed using GP.Hil (Hil+MINY+) and GP.JL (Hil-MINY+) RBCs.

RESULTS

The GP.HF, GP.Mur, GP.Hut, GP.Vw, GP.Kip and GP.Bun frequencies in 1 005 594 individuals were 0·0357%, 0·0256%, 0·0181%, 0·0017%, 0·0009% and 0·0007%, respectively. GP.Hil was found in as four of the 13 546 individuals (0·0295%). Of 137 370 donors, 10 had anti-Hil (0·0073%) and three had anti-MINY (0·0022%).

CONCLUSIONS

Glycophorin variants were relatively rare in Japanese individuals, with the major variants being GP.HF (0·0357%), GP.Hil (0·0295%) and GP.Mur (0·0256%). Only one example of anti-MINY was previously reported, but we found three more in this study.