The Gerbich blood group system (ISBT 020) consists of five high-prevalence antigens, Ge2, Ge3, GEPL, GEAT, and GETI, as well as five low-prevalence antigens, Wb, Lsa, Ana, Dha, and GEIS. Gerbich system antigens are located on glycophorin C and D and form part of the junctional complex of membrane proteins. There are two antibodies to Gerbich system antigens that are sometimes confused for "HTLA" antibodies—anti-Ge2 and anti-Ge3. Both are primarily IgG and demonstrate weakly at the AHG phase.
Disease Association
When an anti-Ge2 or anti-Ge3 is suspected, it is important to differentiate between the two since anti-Ge2 is usually not considered to be clinically significant, whereas anti-Ge3 has been reported to cause hemolytic transfusion reactions (HTR) and hemolytic disease of the fetus and newborn (HDFN). There have also been several reported cases of autoantibodies with Ge2 and Ge3 specificities implicated in autoimmune hemolytic anemia (AIHA).
Treatment
It is important to note that Ge2 antigens are sensitive to enzyme treatment and trypsin/alpha-chymotrypsin, while Ge3 antigens are resistant to all chemical and enzyme treatments; this can assist in determining which specificity is present.
Common Findings
In the case of anti-Ge2, the least incompatible RBCs are typically safe to transfuse, assuming underlying antibodies have been identified or excluded. When anti-Ge3 is present, MMA testing is recommended to determine the clinical significance as Ge:-3 (Ge3 antigen negative) blood is exceedingly rare and should only be given if necessary.
