Pure anti-Doa stimulated by pregnancy

Synonymous nucleotide polymorphisms influence Dombrock blood group protein expression in K562 cells

To gain further insight into ART4 (DO) gene alleles (DO*A, DO*JO1, DO*A-WL, DO*DOYA, DO*B, DO*B-WL, DO*B-SH-Q149K, DO*B-(WL)-I175N, DO*HY1, DO*HY2, DO*DOMR) and evaluate the impact of synonymous nucleotide polymorphisms on protein expression and mRNA accumulation of DO*A-HA, DO*A-SH and DO*B-SH alleles, human erythroleukaemic K562 cells were transducted with variant DO-lentiviral particles and analysed by flow cytometry and quantitative reverse transcription polymerase chain reaction. Monoclonal antibody (MoAb) detection of DO*A-HA and DO*JO1 transductants was lower than DO*A transductants, while detection of DO*A-SH, DO*A-WL and DO*DOYA transductants was higher. Variant DO*B alleles, i.e. DO*B-SH, DO*B-WL, DO*HY1, DO*HY2 and DO*DOMR, showed reduced MoAb binding. The unexpected modifications of protein expression of the DO*A-HA, DO*A-SH and DO*B-SH alleles that differ from the DO*A or DO*B alleles by a single synonymous polymorphism were abolished by reversion, thus implying involvement of these polymorphisms. Depending on the Leu208 codon used, detection level ranged from 1 to 4·14. In the variant alleles resulting from single synonymous polymorphism, mRNA accumulation correlated roughly with MoAbs detection levels, suggesting post-transcriptional regulation. Other than a few reports involving aberrant splicing, the experiments described herein provide the first evidence that synonymous nucleotide polymorphisms can influence Dombrock blood group expression. Such polymorphisms should be taken into account for molecular screening and potential impact on transfusion.

A panel of monoclonal antibodies recognizing GPI-anchored ADP-ribosyltransferase ART4, the carrier of the Dombrock blood group antigens

ART4 (CD297) is a member of the family of toxin-related ADP-ribosyltransferases (ARTs) and is the carrier of the Dombrock blood group alloantigens (Do). Two mouse monoclonal antibodies (MIMA-52 and MIMA-53), and two rat monoclonal antibodies (N0NI-B4 and NONI-B63) were obtained following immunization of mice with human Do/ART4-transfected cells and of rats with human Do/ART4 cDNA, respectively. All four mAbs recognize Do/ART4-transfected Jurkat cells but not untransfected cells by FACS analysis. Staining of Do/ART4-transfected cells by these mAbs was reduced following treatment of cells with PI-PLC, confirming that Do/ART4 is anchored in the cell membrane by linkage to glycosylphosphatidylinositol as predicted from its amino acid sequence. The four mAbs did not react with Gy(a-) (Dombrock null) erythrocytes but agglutinated other red blood cells. By flow cytometric analysis, all mAbs reacted prominently with erythrocytes, and weakly with peripheral blood monocytes and splenic macrophages, but not with B-lymphocytes or T-lymphocytes. The mAbs reacted weakly also with human umbilical vein endothelial cells and the basophilic leukemia KU-812. Immunohistology revealed staining of epithelia and endothelia on sections of tonsils. In FACS analyses NONI-B4 competed with MIMA-52 for binding to Do/ART4-transfected cells and erythrocytes, whereas NONI-B63 competed with MIMA-53. Neither of the mAbs reacted with mouse ART4-transfected cells, but NONI-B63 and MIMA-53 did react with a mouse/human ART4 chimera, indicating that the epitope recognized by these mAbs lies in the C-terminal half of the protein.