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Citation Information : Immunohematology. Volume 27, Issue 3, Pages 89-93, DOI: https://doi.org/10.21307/immunohematology-2019-180
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Published Online: 11-March-2020
The Indian blood group system (ISBT: IN/023) consists of two antithetical antigens: Ina (IN1), which is present in approximately 10 percent of some Arab populations and in 3 percent of Bombay Indians, and its allelic antigen Inb (IN2), an antigen of high incidence in all populations. In 2007, two new high-incidence antigens were identified as belonging to the IN blood group system, namely IN3 (INFI) and IN4 (INJA). The antigens in this system are located on CD44, a single-pass membrane glycoprotein that is encoded by the CD44 gene on chromosome 11 at position p13. The biologic function of CD44 is as a leukocyte homing receptor and cellular adhesion molecule. The Ina and Inb polymorphism represents a 252G>C substitution of CD44, encoding R46P, and lack of IN3 and IN4 results from homozygosity for mutations encoding H85Q and T163R in the CD44 gene. The high-frequency antigen AnWj (901009) has not been assigned to the Indian system, but either is located on an isoform of CD44 or is closely associated with it.