Shigella paradysenteriae organisms were incubated in a solution of trypsin and then removed from the suspension by Seitz filtration. Serologic tests with anti whole Shigella serum indicated that the filtrate contained antigenic material derived from the organisms. When lymph node cells from rabbits not previously injected with Shigella were incubated in vitro with such filtrates and then transferred to irradiated recipients, agglutinins to Shigella appeared in the sera of the latter. The transfer of heated suspensions of cells was not followed by the appearance of agglutinins in irradiated recipient rabbits. Non-irradiated recipients of lymph node cells incubated with the filtrate also developed agglutinin titers, to a lower level than irradiated animals. Agglutinins did not appear in the sera of the majority of non-irradiated recipients of heated cells.

The addition of excess antiserum to either the filtrate or the cell suspension before the incubation of these two materials resulted in a marked reduction in the subsequent agglutinin titers of recipient animals. However, if antiserum was added at the conclusion of the usual 30 minute incubation of cells and filtrate, or even after 5 minutes of incubation, there was no reduction in the agglutinin titers of the recipients.

Cytologic examination of aliquots of a number of the suspensions of cells prepared for transfer revealed that approximately 98 to 99 per cent of the cells belonged to the lymphocytic series.

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