A method is described for the partial restoration of the antibody-binding capacity of meningococcal class 2 outer membrane proteins (40-42 K molecular weight) following denaturation (dissociation) in boiling sodium dodecyl sulfate (SDS). The method relies on the presence of 0.1-0.4% zwitterionic detergent in the electrode buffer during the electroblot transfer of proteins from SDS-polyacrylamide gels to nitrocellulose paper. Meningococcal class 2 proteins which had lost their earlier capacity to bind mouse monoclonal antibodies in the normal blot procedure after SDS-polyacrylamide gel electrophoresis, bound monoclonal antibodies following the addition of the zwitterionic detergent to the blot buffer. Human post-vaccination anti-class 2 protein antibodies reacted with serotype 2a class 2 protein in a similar manner. This simple modification to the electroblot procedure proved helpful in identifying mouse monoclonal antibodies and human antibodies specific for native meningococcal class 2 proteins.