The NOR antigen (Gb5) was derived from the P antigen (ISBT 028, globotetraosylceramide, Gb4), and the P antigen was synthesized on the P SP k sp antigen by the I B3GALNT1 i gene encoded enzyme.1 The P1 antigen was discovered by Landsteiner and Levine in 1927. The P1PK blood group system (ISBT 003) composed of P1, P SP k sp , and NOR antigens has been officially classified by ISBT in 2011. The P SP k sp antigen was first described by Matson in 1959, and the NOR antigen was named after proband Norton in 1982. [Extracted from the article]