FIG. 3.

trans complementation of superantigen-deficient Y. pseudotuberculosis H194. pUC18 and plasmid pCCY12 containing the intact ypmA gene were introduced into superantigen-deficient Y. pseudotuberculosis H194 by electroporation. T-cell proliferation induced by overnight culture supernatants was measured by [³H]thymidine incorporation (34). Each column represents the average of three values ± SD. The nonparametric Mann-Whitney test was used for statistical evaluation of the results, the stimulation index from the wild-type strain being used as the reference. P = 0.05 was the limit of significance. NS, nonsignificant.