Structural and antigenic differences between two types of meningococcal pili

Strains of meningococci, which were shown to be pilated by electron microscopy, could be divided into two groups on the basis of antigenicity and subunit Mr. Strains from group 1 which reacted with monoclonal antibodies directed against gonococcal pili, had pili with subunit Mr similar to that of gonococci which could be detected by radioimmune precipitation or electroblotting. Strains from group 2 failed to react with the monoclonal antibodies and had pili with lower subunit Mr which could only be detected by radioimmune precipitation using polyclonal antipilus antiserum and not by electroblotting.