Generation of recombinant antibodies containing EBV epitopes. (A) Schematic representation of the immunoglobulin heavy chain (HC) and light chain (LC) genes showing the PciI restriction enzyme site used for insertion of the EBV epitope sequences into the C_H2 region of the HC gene. (B) The fully assembled antibody molecule is composed of 2 copies of the LC and 2 copies of the HC containing the EBV epitope. Plasmids expressing the HC and LC of the anti-CD21 antibody (with and without EBV epitopes) were transfected into 293 cells. A western blot analysis of transfected 293 cell extracts was performed under (C) native or (D) reduced conditions for αCD21 antibodies, including epitopes from the EBNA3C (5H11 and 3H10) and the EBNA3B (B9) proteins. An antibody specific to mouse immunoglobulin HC and LC was used to visualize the antibody proteins. In panel C, Ab represents the complete antibody molecule containing 2 HC and 2 LC and * represents other variations of the HC and LC complexes. In panel D, * represents a nonspecific band present in all samples.