Nonspecific Warm Hemolysins of Papain‐Treated Cells: Serologic Characterization and Transfusion Risk

Over a 13‐year period, 130,000 sera were screened for atypical antibodies with untreated and papain‐treated cells. A warm hemolysin of the papain treated screening cells was found in 130 (0.1%) sera. The hemolysin was characterized serologically and its clinical significance evaluated. The hemolysin could be misinterpreted as anti‐H or anti‐HI if preferential lysis of stored red cells was not noted. The hemolysins reacted most strongly with papainized cells, variably with trypsinized cells, and did not lyse red blood cells treated with bromelin or neuraminidase. The hemolysin appeared in a wide variety of clinical conditions and included normal individuals with no correlation to any specific disease process. Transfusions of stored rather than fresh blood were given to 23 patients with no untoward reaction. The phenomenon is concluded to be an in vitro effect creating technical difficulties, but of no clinical significance.