A New Reagent (ZZAP) Having Multiple Applications in Immunohematology

Abstract

A reagent (ZZAP) containing a mixture of 0.1 M dithiothreitol (DTT) plus 0.1% cysteine-activated papain was found to dissociate IgG immunoglobulin from red blood cells (RBC) of patients having a positive direct antiglobulin test (DAT) although this could not be achieved with either chemical alone. In all 67 patients tested, ZZAP treatment of IgG sensitized RBC reduced the strength of the DAT, and in all 52 instances tested, this allowed for accurate Rh phenotyping using slide/rapid tube typing reagents. This included five examples in which spontaneous agglutination that occurred in saline or 6% albumin was eliminated by ZZAP. Thus, all red blood cell typing for Rh-Hr antigens was accomplished using slide/rapid tube reagents making unnecessary the use of saline reactive or chemically modified antisera. Kidd antigen typing is also possible after ZZAP treatment of IgG sensitized RBC. In regard to warm autoabsorption tests, ZZAP treatment of 14 RC samples having a positive DAT proved preferable to heat elution technics since equal or greater amounts of IgG were removed by ZZAP and little or no hemolysis resulted. ZZAP has no effect on ABH, Rh or Kidd antigens but denatures Duffy, MNSs and all Kell antigens tested (K:1-K:7, K:11-K:14, K:18, K:19). This should prove valuable in certain investigations of multiple alloantibodies and, moreover, may allow for better characterization of Kell antigens.