Identification of two new blood group systems, Langereis (LAN) and Junior (JR)

Abstract

Listen

Translate article

Background The high‐prevalence erythrocyte blood group antigens Lan and Jra were first reported in 1962 and 1970 respectively. While both anti‐Lan and anti‐Jra can cause acute transfusion reactions, anti‐Jra is of particular concern in obstetrics as it can cause fatal hemolytic disease of the fetus and the newborn (HDFN). The biochemical and genetic bases of Jra and Lan have not yet been elucidated despite the isolation of two hybridoma secreting human monoclonal antibodies specific for Jra (HMR0921) and Lan (OSK43).Results Using the OSK43 antibody, we were able to immunoprecipitate a single protein from the erythrocytes of a random (Lan+) blood donor. This protein was identified by mass spectrometry as ABCB6, a member of the ATP binding cassette (ABC) transporter family. In order to validate ABCB6 as a novel genetic locus encoding blood group antigens, we first confirmed by immunoblot analysis that ABCB6 was present in the membrane of Lan+ erythrocytes. In contrast, we detected no ABCB6 products in Lan− erythrocytes, suggesting that null alleles of ABCB6 may be responsible for the Lan− phenotype. We then established K‐562 cells stably transfected with a construct encoding ABCB6 and showed that exogenous expression of ABCB6 correlated with cell surface expression of the Lan antigen. Targeted sequencing of ABCB6 in 12 unrelated Lan− individuals identified 10 different null mutations. All these Lan− individuals were either homozygous for a single null mutation or heterozygous for two null mutations in ABCB6, confirming that null alleles of ABCB6 are responsible for the Lan− phenotype. Using the HMR0921 antibody, we similarly purified and identified the ABC transporter ABCG2 as the carrier of the Jra antigen. Analysis of Jr(a+) or Jr(a−) erythrocytes, as well as K‐562 cells transfected with ABCG2 cDNA, showed that the Jra antigen is encoded by ABCG2 and that Jr(a−) erythrocytes lack ABCG2. Targeted sequencing of ABCG2 in 18 unrelated Jr(a−) individuals identified eight different null mutations, which were responsible for their Jr(a−) phenotype, and revealed that the prevalence of the Jr(a−) phenotype in the Japanese and European Gypsy populations is related to the mutations p.Q126X and p.R236X in ABCG2, respectively.Conclusions We demonstrated that the related transporters ABCB6 and ABCG2 specify two new blood group systems called Langereis (LAN) and Junior (JR), respectively. The elucidation of their molecular bases will facilitate the detection of individuals with the rare Lan− and Jr(a−) phenotypes and hence improve their transfusion security and/or their pregnancy follow‐up.