The plasma is split into three aliquots, and each is then adsorbed by the R1R1, R2R2 or rr red cells. These are incubated at 37oC (usually, but, if a "cold" auto-antibody, or a mixed "cold"/warm auto-antibody is suspected, 4oC) for about 20 minutes. The mixture is then centrifuged, and the plasma, if initially in R1R1 red cells, transferred to another aliquot of (packed) R1R1 red cells (if R2R2 then to the next aliquot of R2R2 cells, and, if initially rr red cells, to the next aliquot of rr red cells). The incubation is repeated, as is the centrifugation and the transfer to the next aliquot of red cells. What Malcolm describes here is how we did it at my reference lab. We made our own red cell stroma concoctions using 3 different cell types--the same as Malcolm described. Then after absorbing we would test the adsorbed plasma with our regular antibody panels.