Serological and molecular analyses of a patient with anti-G and anti-D due to alloimmunisation during her pregnancy.

Dear Sir, G antigen (Rh12) is expressed on red blood cells that carry D and/or C antigen1-3. Serine is the critical amino acid for G antigen expression. Anti-G can cause haemolytic disease of newborn, which is rare, but responsible for neonatal morbidity and mortality. However, Anti-G antibody is difficult to distinguish from anti-D in combination with anti-C. Accurate identification of these antibodies is important in the clinical management of pregnancies. Here, we describe a 76-year old, gravida-3, para-3, female patient with AB RhD negative D− C− E− c+ e+, who was positive for antibodies that are routinely screened because of a potential need for transfusion. Her husband's and son's blood group were B RhD positive D+ C+ E+ c+ e+ and B RhD positive D+ C+ E− c+ e+, respectively. The antibodies in the patient's serum were identified by an 11-cell screening panel using a gel column method in a DiaMed-ID LISS/Coombs system (Cressier, Switzerland) (Table I). There were 4+ reactions with all D+ and/or C+ red blood cells. The serological reactivity implied that the red blood cell antibodies resembled IgG anti-D and anti-C. However, anti-G appears serologically identical to anti-D and -C. Therefore, differential adsorption-elution studies were performed to define the identification of the antibodies in the woman's serum. Her serum was adsorbed with Ccdee cells; the adsorbed sera were tested against selected red blood cells (O type, ccDEE, ccDEe, and ccDee) using the indirect antiglobulin method. There were agglutination reactions of 2+ or 4+ with all D+ red blood cells, indicating that anti-D were present in the serum. In another test, the woman's serum was adsorbed with ccDEE cells, then the adsorbed sera were tested against O type Ccdee. No reactivity was seen with Ccdee red blood cells, which excluded the presence of anti-C. The elution from the adsorbed ccDEE cells reacted with D+ and/or C+ red blood cells. These results indicate that anti-G was present in the elution. The woman's antibodies were, therefore, anti-D and anti-G, but not anti-C. RHD and RHCE genotyping were performed by polymerase chain reaction (PCR with sequence-specific primers (SSP) and PCR restriction fragment length polymorphism (RFLP). Briefly, multiplex PCR-SSP was used to detect the RHD-specific polymorphisms located in RHD intron 4 and RHD exon 7. Samples negative