抄録
When Shigella flexneri lb, 3 and 4b were cultured in a broth containing type or group factor serum, variants deficient of the type or group antigen could be easily obtained. S. flexneri lb and 4b were converted to S. flexneri 3 with the loss of their respective type antigens. It was found that the presence of group 6 antigen was an indispensable condition for the occurrence of these variations. And type III antigen and group 6 antigen of S. flexneri 3 never underwent loss variation independently of each other.
These two antigens were more unstable against alkali than other type or group antigens of S. flexneri, losing their serological specificity when treatedwith a 0.5per cent NaOH solution at 0ªC for one hour.
