Filtration algorithm of HLA antibody-positive donors and antibody-negative controls. The algorithm depicts the experimental design of the donors employed for manufacture of RBC units that underwent experimental filtration using filters B, P, or M or standard LR (Pall BPF4 LR filter). Please note that there are 4 antibody-negative male controls per experimental filter and 4 antibody-negative donors, 2 male and 2 female for the BPF4 LR filter.