Expression Of B7-H1, B7-H3, B7-H4in The Small Intestine Of Normal And X-ray Irradiated Mice

Objective:To investigate whether small intestinal epithelial cells express B7-H1, B7-H3, B7-H4proteins and whether the expression of B7-H1, B7-H3, B7-H4change in radiation-induced small intestinal injury.Methods:C57BL/6mice were divided into8Gy,15Gy and non-irradiated normal control groups randomly. The irradiated groups received total body irradiation (TBI) with X-rays at a dose rate of200cGy/min. At several time points mice were sacrificed and ileum tissue were harvested. The injury of small intestine were observed by HE staining. The location and expression levels of B7-H1, B7-H3, B7-H4proteins and their co-location with Lysozyme C or CD3+T cells were detected by immunohistochemistry, immunofluorescence and western blotting.Results:(1) Paneth cells expressed B7-H1and B7-H4. B7-H4expression was also observed in intestinal central lacteal. B7-H3expression was not observed in intestinal epithelium.(2) The weight loss was more obvious, the survival time was shorter and the gastrointestinal symptom was more severe in15Gy group compared to8Gy group. While intestinal injury caused by8Gy X-ray TBI was recoverable, intestinal injury caused by15Gy X-ray TBI seemed unrecoverable.(3) B7-H1was not released with lysozyme.(4) The expression level of B7-H1protein decreased with a transient increase post irradiation. The expression level of B7-H4did not change obviously.(5) CD3+T cells were observed at the bottom of the crypt post irradiation.Conclusion:Paneth cells expressed B7-H1and B7-H4proteins. B7-H4was also expressed in intestinal central lacteal. B7-H3expression was not observed in normal intestinal epithelium. B7-H1was not released through degranulation by Paneth cells. Ionizing irradiation changed the expression levels of B7-H1in small intestine. Ionizing irradiation induced the infiltration of CD3+T cells at the bottom of the crypt.