A case report of a rare p phenotype individual and a review of molecular biological analysis of p phenotype in the Chinese population.

Objectives: To explore the serological characteristics and molecular mechanisms of an individual with the p phenotype in the Chinese population by analysing the serological and genetic background.

Background: The p phenotype, which lacks all antigens in the P1PK blood group system, is extremely rare in the Chinese population. Individuals with the p phenotype typically produce anti-PP1P^k antibodies. The P1, P^k antigens belong to the P1PK blood group system, while the P antigen is part of the GLOB blood group system. The antigens in the P1PK system are synthesised by α1,4-galactosyltransferase (α4Gal-T), while the antigens in the GLOB system are produced by 3-𝛽-N-acetylgalactosaminyl-transferase (β3GalNAc-T1). These glycosyltransferases are encoded by the A4GALT and B3GALNT1 genes.

Materials and methods: Serological techniques were employed to determine the blood types and antibodies of an individual with the p phenotype. Additionally, first- and third-generation sequencing methods were used to analyse the A4GALT and B3GALNT1 genes in the sample.

Results: The serum from the tested individual showed positive reactions with all red blood cells (RBCs) from two sets of panel RBC reagents, while it reacted negatively with a confirmed p phenotype red blood cell. The antibodies in the serum exhibited IgM + IgG properties, with IgG being the predominant type. The antibody titers at room temperature, 37°C, and 4°C were 128, 64, and 256, respectively. Sequencing analysis revealed a homozygous mutation in the A4GALT gene at rs5751348: G > T; c.343A > T; c.903C > G, while no mutation was detected in the B3GALNT1 gene.

Conclusions: The tested individual exhibited the p phenotype and likely produces anti-PP1P^k antibodies. The allele carrying rs5751348: G > T; c.343A > T; c.903C > G in the A4GALT gene has been provisionally designated A4GALT*02 N.28 (pending official recognition by ISBT).