Murine monoclonal antibodies can be used to type RBCs with a positive DAT

RBCs with a positive DAT due to IgG coating require the use of directly agglutinating reagents or treatment with chemicals to remove sufficient IgG to permit typing of the RBCs with antisera that require use of the IAT. In this study we demonstrate that murine IgG MoAbs to human RBC antigens can be used as an alternative if the anti-mouse IgG is neutralized or affinity purified to prevent cross-reaction with cell-bound IgG. We performed DATs on RBC samples coated with IgG in vivo and in vitro, comparing two anti-human IgG reagents (Organon Teknika, Durham, NC, and Ortho-Clinical Diagnostics, Raritan, NJ) with two affinity-purified anti-mouse IgG reagents (The Binding Site, San Diego, CA, and Sigma, St. Louis, MO), and one non-purified anti-mouse IgG reagent. The affinity-purified anti-mouse IgG reagents were nonreactive with the four in vitro sensitized RBC samples and were nonreactive with 8 of 11 in vivo sensitized RBC samples. Non-purified antimouse IgG and both anti-human IgG reagents reacted with every sample. Use of murine MoAbs to antigen type RBCs coated with human IgG is reliable only when the anti-mouse IgG reagents have been affinity purified or neutralized to prevent cross-reactivity. Our results also show the importance of including a saline/RBC control as well as an anti-mouse IgG/RBC control. Murine MoAbs are valuable reagents and we have applied them successfully in typing patients' RBCs that have a positive DAT.