Antigens that are similar in apparent molecular weight to gonococcal outer membrane protein III.

Two immunoglobulin G monoclonal antibodies (MAbs) were produced by using purified outer membranes and whole gonococci as immunogens. These MAbs recognized antigens with similar apparent sizes (30 to 31.5 kilodaltons [kDa]) in several pathogenic and nonpathogenic neisseriae. In gonococci, these 30- to 31.5-kDa components, although similar in subunit size to outer membrane protein III (P.III), are distinct due to their differences in electrophoretic migration-modification by 2-mercaptoethanol and their cellular location. The two 30- to 31.5-kDa moieties are denoted by MAb2 and MAb3, respectively, by which they are identified. The differentiating characteristic of these three antigens (P.III, MAb2, MAb3) is their change or lack of change in electrophoretic mobility in the presence versus absence of 2-mercaptoethanol; P.III migrates less rapidly, MAb2 does not change, and MAb3 migrates more rapidly. Both the epitopes that were reactive with MAb2 and MAb3 were resistant to proteolytic treatment of intact gonococci; neither epitope was detected on whole, unfixed gonococci by immunofluorescence. Both MAb2 and MAb3 epitopes were represented uniformly among pathogenic neisseriae (except group Z meningococci) and less regularly among nonpathogenic neisseriae.