ANTIGENIC VARIATIONS IN SHIGELLA FLEXNERI 1b, 3 AND 4b

Type and group antigens of Shigella flexneri are not stable.Antigenic variations are common.The variation of type antigens of S. flexneri cultures is a modified form variation, its essential features being a loss of type antigen and an increase of group antigen.The variation resulting in loss of antigens was studied by Takita (1), Boyd(2), Weil, Farsetta and Knaub(3), Veazie(4) and Ewine(5).In addition to the modified form variation resulting in the loss of type antigen, certain S. flexneri cultures were found to be subject to a second modified form variation involving group antigens.This was observed by Nakamura(6,7), Ewing(5) and Cooper, Keller and Walters(8).Besides these two, a third antigenic variation was found in S. flexnen lb by Sasagawa and Koizumi(9) and Nakamura(6).They observed both in vivo and in vitro that S. flexneri lb is converted into S. flexneri 3 (III : 3, 4, 6).Antigenic variations have been induced in many different bacteria with great selectivity in the presence of the antiserum.A variant with a changed antigen can be obtained when a strain is cultured in a medium containing a specific antiserum.By this method antigenic transformation from S. flexneri type I to type III was accomplished using specific antiserum to type I.It was observed that there is a close relation between type III antigen and group 6 antigen and further that not only type I but also type IV can be converted to type III.