Pretreatment with Daudi cells eliminates anti-CD47 monoclonal antibody interference in immunohematology testing

Anti-CD47 monoclonal antibodies have increasing clinical applications in the treatment of cancer. However, anti-CD47 monoclonal antibodies interfere with immunohematology testing in patients who require blood transfusion. As the current approaches to removing any interferences have technical problems, new methods need to be developed to resolve anti-CD47 interference in immunohematology testing.

We evaluated the Daudi cell line for the adsorption of free anti-CD47 monoclonal antibodies from patients' plasma to facilitate immunohematology testing in patients treated with anti-CD47 monoclonal antibody. CD47 expression was identified on the Daudi cells using flow cytometry and confocal microscopy. Next, we tested the ability of intact Daudi cells mixed with simulating plasma and clinical samples to achieve efficient removal of interfering anti-CD47 monoclonal antibodies. The indirect antiglobulin test was used to verify whether interference from anti-CD47 monoclonal antibodies in plasma was eliminated and whether the detection of other irregular antibodies was affected. The effect of eliminating interference was also investigated in relation to the time that the Daudi cells were stored after having been fixed with paraformaldehyde.

CD47 expression was higher on Daudi cells than on red blood cells. Analysis of the indirect antiglobulin test results revealed that anti-CD47 monoclonal antibody-treated patients' plasma absorbed by Daudi cells for 15 min at 37°C could completely prevent the interference of anti-CD47 monoclonal antibodies in immunohematology testing while the detection of the tested antibodies, including anti-D and anti-K, was unaffected.

By decreasing the incubation time, we discovered that interferences in samples with agglutination strengths below 2+ could be eliminated after incubation for 5 min. Of importance, Daudi cells can be preserved with 4% paraformaldehyde for 14 days as short-term storage reagents. This is the first study in which Daudi cells were used to effectively resolve the interference of anti-CD47 monoclonal antibodies in pretransfusion tests.