MNS antigen system

The MN blood group in humans is under the control of a pair of co-dominant alleles, LM and LN.

[citation needed] The MN blood group system is under the control of an autosomal locus found on chromosome 4, with two alleles designated LM and LN.

Phenotypic expression at this locus is codominant because an individual may exhibit either one or both antigenic substances.

Anti-M and anti-N antibodies are usually IgM and are rarely associated with transfusion reactions.

[citation needed] Anti-N is sometimes seen in dialysis patients due to cross-reactions with the residual formaldehyde from sterilizing the equipment.