The relative expression levels of Toll receptor, immune deficiency (IMD) and lysozyme mRNAs were measured in the gills of the white shrimp (), which were bacterial suspension (low concentration group:Vibrio , respectively. The mRNAs were detected quantitatively with real-time PCR technology at different times after challengerelative expression levels of the Toll receptor and IMD of the shrimp injected with saline did not significantly change. However, trelative expression levels of lysozyme mRNA significantly increased at 36 h after injection. The peaks of the relative expression of the Toll receptor, IMD and lysozyme mRNAs in gills of the shrimps appeared at 24, 42 and 36 h The vibrio dosage did not affect the timing of the peak of the gene expressions. However, Vibrio dosage significantly changed sizes of the peaks of gene expressions (<0.05). The peaks of the gene expression were in the order of high concentration group, the low concentration group and the saline-injected group. In the early stage of challenge, the expression level of the Toll receptor, but not IMD and lysozyme mRNA, was significantly downregulated. Compared with that before challenge, the level of Toll receptor mRNA expression was significantly lower at 2 and 3 h, respectively, in the . The IMD and lysozyme mRNA expression levels of the high concentration group were significantly upregulated at 36 and 12 h, he IMD and lysozyme mRNA expression levels of the low concentration group significantly increased at 42 and 24 h, relative expression levels of the Toll receptor, IMD and lysozyme mRNA in the gills of challenge. Changes in the expressions of these genes depended on the challenge time and challenge dosage of