Veterinary Immunology and Serology

Rh SYSTEM AND ERYTHROBLASTOSIS FETALIS

Rh system

• Levine and Stetson (1939) demonstrated a new antibody in the serum of women who developed reaction following blood transfusion and she recently delivered stillborn baby with hemolytic disease.
• Landsteiner and Wiener (1940) found that rabbit antiserum to rhesus monkey RBC agglutinated RBC of 80% normal people. This antigen or RBC is called Rhesus or Rh factor.
• Very large number of antigens are detected in Rh system, they cross react and weakly immunogenic except ‘D’ or Rho antigen which is most powerful antigen and responsible for majority of Rh incompatibility reaction. Thus people are divided into Rh positive and Rh-negative groups.
• Rh antigens are determined by three pair of closely linked allelomorphic genes (Cc, Dd, and Ee).

Erythroblastosis fetalis

• When Rh-negative women carries Rh-positive fetus (when husband is Rh positive), she develops antibodies to Rh antigen as fetal blood enter to maternal circulation (minor transplacental leakage occur during pregnancy but during delivery large amount of fetal blood enter into maternal circulation).
• Mother develops immunity during first pregnancy.
• During subsequent pregnancy, Rh antibodies (IgG class) pass from mother to fetus and cause haemolysis or jaundice.