Résumé
【Objective】 To summarize the serological characteristics of B311 subtype and analyze its gene sequence. 【Methods】 PCR-SSP, direct sequencing of promoter 5'end and 1-7 exons were performed on 4 samples, which were consistent by forward and reverse blood typing via automatic blood type system, but presented mixed agglutination of B antigen via test tube method. 【Results】 The 4 samples, with the presence of B antigen 4+ in the microcolumn gel card, were determined as the blood group of B or AB by the automatic blood type system according to the consistency between forward and reverse blood typing. While mixed agglutination of B antigen 2+ -3+ was observed by test tube method. Among the 4 samples, 2 were B/O01, 1 B/O02, and 1 AB by PCR-SSP. No mutation was found in B101 by direct sequencing of exons 1-7, and a heterozygous mutation of -35--18delGGCGGAAGGCGGAGGCCG was found at the 5'end of the promoter. 【Conclusion】 The -35--18del base mutation at B allele is the molecular genetic mechanism of B311. The reduced promoter activity leads to B3 serological performance. The automatic blood type system has certain limitations in detecting B311 subtype.