Rare Anti-f(ce) Detected During Cross-Matching

The f(ce) antigen is a compound Rh antigen expressed with both c- and e-antigens coded in same haplotype. Detection of anti-f(ce) has rarely been reported due to both its rarity and difficulty to analyze. Here, we report anti-f(ce) detected during cross-matching, which was confirmed by two further tests.

A 66-year-old male who had never received a transfusion, was diagnosed with an abscess of the hip joint bursa in a previous institution. During therapy about 50 - 60 days ago, he received a total of 4 units of packed red blood cells (pRBC). Soon, he was transferred to our institution for an operation, and a post-operation pRBC transfusion was ordered. An initial antibody screening test (AST) using 2 cell-lines showed all negative results, but a subsequent cross-matching test showed incompatibility to 2 of 7 donor RBCs. Thus, an additional AST using 3 cell-lines and a further identification test revealed anti-f(ce) without any coexistent antibody. To reconfirm this antibody, "Rh CcEe subgroup profiling of incompatible donor RBCs" and "Re-AST using the patient's plasma after adsorption to incompatible pRBC" were planned.

First, among all 18 cross-matched units of pRBCs, 16 units were compatible with the patient's serum, but 2 units were not. These incompatible units showed CcDe and cDEe phenotypes, respectively, suggesting that they might contain c- and e-antigen genes in cis. Second, Re-AST using the remnant plasma after adsorption to 1 (CcDe) of the above 2 incompatible units persistently showed anti-f(ce) in "3+". However, a modified test adding 1 more adsorption step that took 7 hours at 37℃ following the above typical method showed the same result but with a decreased strength "±".

All pRBCs showed suitable Rh phenotypes to their cross-matched results, supporting that f(ce) antigen exists only when c- and e-antigens are coded in same haplotype. Adsorption of anti-f(ce), which consists of mainly IgG, seems to require a longer incubation time compared to the typical method. Further studies for the affinity and avidity of anti-f(ce) and optimal conditions to maximize these features are needed.