Rh Blood Group System.

Rh Factor.

ABO blood type is further differentiated by a + or – sign. This positive or negative sign refers to the presence or absence of another blood group system antigen called Rh factor.

Rh system.

Rh blood group system is defined on the basis of Rh factor present on the surface of RBC. This system is named Rh after Rhesus monkey, because its antigen was first discovered in it by Landsteiner in 1930s.

Gene.

Rh blood group system is encoded by three genes C, D and E, which occupy two tightly linked loci. Loci. Alleles of gene D occupy one locus called locus D, while genes C and E alternatively occupy the other locus. The D locus is of prime importance.

Gene D.

Gene D has two alleles, D and d. D is completely dominant over d. Rh+ Persons having genotype DD or Dd have Rh factor on their RBC and are Rh+. Rh-. Persons with genotype dd do not have Rh factor and are Rh-. Rh antibodies Production. Unlike the naturally occuring anti – A and anti – B antibodies of ABO system, anti – Rh antibody production requires a stimulus by the human Rh antigen itself. An Rhperson does not produce anti – Rh antibodies unless he is exposed to Rh antigen. Blood Transfusion. Rh+ donor is totally incompatible for Rh- recipient. If an Rh- person receives Rh antigen through wrong Rh+ blood transfusion, he will begin to produce anti – Rh antibodies against Rh antigens. Rh- blood, clear of any anti – Rh antibody from a donor who has never been exposed to Rh antigen can be transfused to Rh+ recipient