Protein antigens were prepared from rough strains of Salmonella typhimurium and S. dublin by
phenol and veronal-buffer extraction. It was shown that the in vitro migration of peritoneal exudate
cells from guinea pigs that were immunized with rough avirulent mutants could be inhibited
effectively with these antigens.
The cells obtained from S. typhimurium-immunized guinea pigs were also sensitive to S. dublin
antigens and vice versa.
A degree of sensitivity and inhibition could be demonstrated consistently in a group of
immunized guinea pigs. However, the variation in samples, even from among individual animals that
had survived challenge, was so great that it precludes the use of the macrophage migration technique
as a routine standard assay procedure for immunity.