Immunological analyses and gene therapy in chronic colitis of IL-12p40 transgenic mice

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(Aims) : To investigate the roles of IL-12p40 in chronic intestinal inflammation, we generated IL-12p40 transgenic mice using T3^b promoter and determined the restricted expression of IL-12p40 to intestinal epithelial cells. (Methods & Results) : T3^b-IL-12p40 trans genic mice were produced by DNA microinjection method. Transgene contains T3^b promoter, rabbit B globin exon and intron, mouse IL-12p40 cDNA and rabbit beta globin polyA.As a result of screenings by PCR, six founders carrying this transgene were produced. Their phenotypes were almost normal. These mice were backcrossed with C57BL/6 mice, and next generations were obtained in four founders, line #9, #13, #20 and #24. The copy number of the trans gene in mouse genome was determined by Southern blot analysis. As judged from hybridizing intensity of bands, the four transgenic mice carry less than 10 copies of the T3^b-IL-12p40 construct. Northern blot analysis and RT-PCR were performed to examine mRNA expression derived from trangene. IL-12p40 mRNA was detected in large and small intestine of the transgenic mice. Except for gastrointestinal tract, mRNA derived from transgene was not detected in major organs including thymus. And immunohistochemical analysis of the large intestine derived from transgenic mouse and negative littermate were conducted using IL-12 (p40/p70) monoclonal antibody. The epithelial cells of the large intestine in transgenic mice was mainly stained. Colitis was induced in T3^b-IL-12p40 transgenic mice and negative littermate by 1.5% dextran sulfate sodium. The differences of colitis score between transgenic mice and negative littermate were not significant.