Impact of genetic variation in the ABCC4 gene on PEL expression levels. (A) Flow cytometry profiles of PEL expression in different red cell variants of ABCC4. (B) Corresponding geometric mean of fluorescence (GMFI) of PEL antigen expression in different variants of ABCC4. PEL expression was analyzed using an anti-PEL eluate. Heterozygous variants in ABCC4 were selected from our own RBC bio-collection. All mutations were confirmed by Sanger sequencing. Statistical analyses for significance were performed using the Mann-Whitney test. **P < .005.