Corresponding immune-blots confirm weakened expression of ABO, identified by PCA of serologically identified donors. PCA plot displayed by sample identification (A) and matching immunoblotting with anti-H, anti-A, and anti-B. Anti-A and anti-B dot blots (B) demonstrated weakened glycoprotein expression observed as outliers in the PCA plot. Weakened expression was accompanied by slight to moderate increases in H antigen in most samples.