IFNG and infection: Therefore, in approach II we first compared expression of Group 1 genes in mice after sublethal pYV+ (Table 1, column 1) and lethal ΔyopH infection (Table 1, column 4) which resulted in similar splenic bacterial counts 1 day p.i. The data revealed Group 1A, which included genes with comparable expression after sublethal pYV+ and lethal ΔyopH infection such as, IFN-γ and histidine decarboxylase, and Group 1B, which included genes which were expressed less after lethal ΔyopH infection as compared with sublethal pYV+ infection.