The influence of storage and leukocyte depletion on the antigen densities of FY1, FY2, MNS3 and MNS4 measured by flow cytometry

Red blood cell (RBC) antigens may present changes in density during storage and leukocyte reduction. We evaluated the influence of these variables on FY1, FY2, MNS3 and MNS4 antigens using quantitative flow cytometry (FCM). Forty-eight RBC units were divided into two sub-units each immediately after collection. One of them was leukocyte reduced before storage. Antigen expression was analyzed on days 1 and 35 of storage by gel-centrifugation and FCM. Three RBC samples were submitted to papain and bromelin treatment. The gel-centrifugation test could not detect any influence of storage or leukocyte reduction. However, by FCM, a wide variation of antigen density among the donors was found. Leukocyte depletion did not change the antigen density but after storage, expression of FY1 and MNS4 showed a slight decrease. Median antigenic density of FY1 was 11,332 in FY1,2 and 23,436 in FY1,-2 donors. FY2 presented 7204 and 7868, respectively. MNS4 had 100,589 and 214,340 sites in donors MNS3,4 and MNS-3,4, respectively, and MNS3 had 10,389 and 21,122 sites, respectively. After enzyme treatments none of the antigens could be detected. FCM was a reproducible technique, suitable for the quantification of the antigens studied in RBC concentrates stored and leukocyte reduced in conditions normally used for blood transfusion.