Importance of complement source in bactericidal activity of human antibody and murine monoclonal antibody to...

The bactericidal activity of human antibody and murine monoclonal antibody to meningococcal group B polysaccharide was investigated as a function of the complement source. The immunoglobulin M murine monoclonal antibody 2-2-B was shown by several different methods to be highly specific for meningococcal group B and Escherichia coli K1 capsular polysaccharides. It had strong bactericidal activity in conjunction with either rabbit or human complement, but gave a higher titer with rabbit complement. A strong prozone was observed in each case. Human postvaccination antibody to meningococcal group B polysaccharide was strongly bactericidal with rabbit complement, but had little or no bactericidal activity in conjunction with human complement. Antibodies in adult normal human sera that were bactericidal with rabbit complement were also found to be predominantly directed against the meningococcal group B capsular polysaccharide. Human antibodies that were bactericidal with human complement appeared to be primarily directed against noncapsular antigens.