Comprehensive analysis of Lewis antigen expression patterns in a Chinese blood donor cohort

BACKGROUND AND OBJECTIVES: To characterise FUT2 and FUT3 haplotype and genotype frequencies among 529 Shanghai Han voluntary blood donors, and quantify erythrocyte Leᵃ and Leᵇ expression via flow cytometry. This study extends the established Seʷ/c.418A>T partial-secretor model to a large Chinese cohort using combined sequencing and quantitative red cell Lewis antigen flow cytometry. MATERIALS AND METHODS: Routine serological ABO grouping was performed. Flow cytometry was used to quantify Leᵃ and Leᵇ mean fluorescence intensity (MFI). Sanger sequencing combined with thymine-adenine (TA) cloning was applied to resolve FUT2/FUT3 cis-haplotypes. Owing to marked skewness and heteroscedasticity of MFI data, non-parametric Mann-Whitney U tests with Bonferroni correction were used for subgroup comparisons. RESULTS: A total of 1046 FUT2 alleles were genotyped: secretor (Se, n = 575, 54.3%), weak-secretor (Seʷ, n = 443, 41.9%), non-secretor (se, n = 28, 2.6%), with eight novel sequence variants. For FUT3, 1053 alleles were resolved: functional (Le, n = 806, 76.2%), loss-of-function (le, n = 247, 23.3%), alongside five novel variants (0.5%). Seʷ homozygosity elevated Leᵃ and reduced Leᵇ in carriers with functional FUT3. Considerable inter-individual variability persisted even among donors with identical ABO-FUT2-FUT3 genotypes. CONCLUSION: Erythrocyte Lewis antigen abundance is primarily governed by competitive substrate utilisation of a common type 1 precursor glycan by FUT2 and FUT3 glycosyltransferases. The residual heterogeneity indicates additional host factors beyond these three loci. This study validates the classic Seʷ partial-secretor model in a Chinese cohort and provides population reference data, rather than reporting unrecognised biosynthetic pathways.