Detection of multiple passively acquired alloantibodies following infusions of IVRh immune globulin

BACKGROUND: Passively acquired blood group alloantibodies are detected regularly after infusions of IV Ph immune globulin (RhIG) for the treatment of immune thrombocytopenic purpura (ITP) in D+ patients. STUDY DESIGN AND METHODS: Blood samples from 16 D+ patients with ITP were tested after treatment with IV RhIG for the presence of passively acquired alloantibodies. Similar studies were conducted for three D- patients after injections of IM RhIG for Ph immunoprophylaxis. Four production lots of IV RhIG and 2 lots of IM RhIG were tested for the presence of alloantibodies. RESULTS: All 16 D+ patients with ITP developed a positive DAT, as well as positive antibody detection test results, after infusions of IV RhIG. All postinfusion plasma samples contained anti-D, as well as one or more additional antibodies, usually anti-C, -E, -G, -V, or -Fy(a). Eluates from patients' RBCs with positive DAT results contained multiple passively acquired alloantibodies. Multiple alloantibodies were detected in samples of different production lots of IV RhIG or IM RhlG. No acute transfusion reactions were observed in five D+ patients with ITP who had been treated with IV RhlG and had been given serologically incompatible D+ RBCs. After injections of IM RhIG, the only passively acquired alloantibody detected was anti-D. CONCLUSION: Plasma samples from D+ patients with ITP treated with IV RhIG regularly contained anti-D and multiple other passively acquired Rh, Duffy, or Kidd system alloantibodies. Postinfusion RBC samples all had positive DAT results with eluates containing anti-D and multiple other Ph, Duffy, or Kidd system antibodies. The consistent detection of multiple passively acquired alloantibodies after IV RhIG, in contrast to the detection of anti-D only after IM RhIG, reflects the immediate effect of the entire (bolus) dose of RhIG by the IV route, the dose for treating ITP that is approximately 10 times the dose for Rh immunoprophylaxis, and the expected serologic incompatibility with recipients' D+ RBCs.