Pathomechanism of cellular infiltration in the perivascular region of several organs in SAMP1/Yit mouse.

We investigated the histological changes of extra-intestinal organs, such as the liver, kidney, lung and pancreas in SAMP1/Yit mice, a human Crohn's disease model, Using immunohistochemical techniques. The perivascular cellular infiltration was detected around the small vessels after 30 weeks. These infiltrating cells consisted of many CD4-positive T-lymphocytes, and small numbers of CD8- positive T-lymphocytes and IgG-positive B-lymphocytes. MAdCAM-1 and VCAM-I were detected in vascular endothelial cells in non-affected regions of 13 and 20 week-old, as well as in the affected regions showing perivascular cellular infiltration after 30 weeks. In addition, integrin alpha 4 beta 7 was detected oil these infiltrating cells in the perivascular regions after 30 week-old. LT-beta and IL-12, cytokines of the Th-1-type immune response, were not observed in these affected regions. However, IL-4, one of the cytokines of the Th-2-type immune response, was detected on the perivascular infiltrating cells after 30 week-old. These results revealed that the changes in extra-intestinal organs were mainly caused by infiltration of CD4-positive T-lymphocytes into the perivascular regions in SAMP1/Yit mice. These Cellular infiltrations were thought to be initiated by adhesion of CD4-positive T-lymphocytes to the endothelial cells mediated by MAdCAM-1 and integrin beta 7. Immunohistochemistry for Th related cytokines indicated that the perivascular cellular infiltration was developed by the Th-2-type immune response in the extra-intestinal organs of SAMP1/Yit mouse. KEY WORDS: cell infiltration, pathomechanism, SAMP1/Yit mouse.