Attachment of biotinylated antibody to red blood cells: antigen-binding capacity of immunoerythrocytes and their susceptibility to lysis by complement.

A biotinylated monoclonal antibody (mAb) to human IgM (b-anti-IgM) has been attached to human red blood cells (RBC) by two different approaches. The first method is performed with biotinylated RBC (b-RBC) and involves stepwise binding of streptavidin (SA) to b-RBC followed by addition and binding of specific b-anti-IgM or b-IgG. b-RBC were prepared with differing input levels of biotin N-hydroxysuccinimide ester (BNHS). At moderate BNHS levels (100 microM) the resulting b-RBC (designated b4-RBC) bound 50,000 molecules of b-IgG after treatment with SA. However, at high BNHS levels (> 1000 microM) the resulting b-RBC bound b-IgG poorly, presumably due to multivalent binding of each SA to several biotins in close proximity on the RBC. b-RBC prepared at high BNHS inputs (but not b4-RBC) were lysed by serum plus SA. Stepwise attachment of b-anti-IgM to SA-coated b4-RBC allows binding of up to 6 x 10(4) molecules of b-anti-IgM/RBC. The second method is based on attachment of b-anti-IgM to RBC via CR1, the primate RBC complement receptor. The SA-biotin system is used to prepare bi-specific mAb complexes (heteropolymers) in which a biotinylated mAb to CR1 is cross-linked with b-anti-IgM via SA. Binding of these heteropolymers to RBC via CR1 is specific and saturable and can facilitate binding of up to 2500 molecules of b-anti-IgM/RBC.(ABSTRACT TRUNCATED AT 250 WORDS)