Antigenic structures of Salmonella flagella. I. Presence of an antigenic determinant exposed at one end of flagellar fragments.

Salmonella flagellin, which is a constitutional subunit of the flagellum, was shown to have antigenic determinants distinct from its own serotypic ones. These antigenic determinants were found to be common to flagellins from the so-called g-complex serotypes, such as fg, mt, gm, gt, gp and gmptu, but not to those from other serotypes, such as a, i or enx. Rabbits immunized with flagellin of serotype "fg" produced anti-"fg" flagellin antibodies. Only about 20 percent of these corresponded to the serotype determinants of the "fg" on the surface of the flagella, and the remaining 80 percent reacted with the flagellin of the unrelated serotype "mt", and corresponded to the distinct determinants common to the flagellin molecules. These antigenic determinants were detected by the immunoferritin technique at only one, not both, terminals of the flagellar fragments, suggesting that a unidirectional arrangement of flagellin subunits in the flagella may expose the inherent conformation of the subunits at only one end of the flagellum.