The Study On Immune Function Of Urea Transporter-B Gene Knockout Mice

We inquired into the influence of UT-B gene on immune function using urea transporter-B (UT-B) gene knockout mice (UT-B-/-) and their littermate wild-type (WT) mice as control.70pairs of UT-B gene knockout mice and wild-type control mice were screened by a gene identification method and were divided into two groups for testing.15pairs of UT-B gene knockout and wild-type control mice were taken out from the first group and used for detecting expression of UT-B protein in spleen and measuring the index of immune organs. We also conducted spleen lymphocyte transformation tests and pattern analysis of lymphocytes in spleen and peripheral blood of the mice by flow cytometry.20pairs of UT-B gene knockout and wild-type control mice were taken out from the second group were used for tumor-bearing tests and morphological observations of tumor tissues. We measured UT-B protein expression in spleen of UT-B gene knockoutmice and WT controls by Western blotting and found that UT-B protein, with molecular weight of41-54KD, was expressed in WT spleen but not in UT-B gene knockout spleen. The spleen index of UT-B gene knockout mice was2.76, while wild-type mice was3.71, so we concluded that spleen index of UT-B gene knockout mice was significantly lower than that wild-type mice (P<0.01). In the lymphocyte transformation tests, spleen lymphcytes were stimulated with concanavalin A (Con A) and we found that UT-B gene knockout mice possess higher transformation rate than WT controls(2.7to1.8). When spleen thymocytes were stimulated with LPS, however, the transformation rate of knockout and WT were3.62to3.22. Spleen lymphocyte transformation rate of UT-B gene knockout mice was significantly greater than that of UT-B wild-type mice(P<0.01). Flow cytometry results showed percentage of CD4+T cells in UT-B gene knockout spleen was15.18%, greater than that of wild-type mice(P<0.01). Meanwhile, percentage of CD8+T cells in UT-B gene knockout spleen was3.16%, greater than that of wild-type mice as well(P>0.05). For B cells, however, total number of B cells in UT-B gene knockout spleen was lower than that of WT (.P>0.05). In tumor-bearing test, we found that tumor-inhibition rate of UT-B gene knockout mice was55.1%, and the spleen indexes of tumor-bearing knockout and WT mice were respectively4.7and4.3, and the difference was not significant (P>0.05); Percentage of CD4+T cells in spleen and peripheral blood of tumor-bearing UT-B gene knockout mice was30.71%(P<0.01), greater than that of tumor-bearing UT-B wild-type mice. Percentage of T cells in spleen and peripheral blood of tumor-bearing UT-B gene knockout mice was37.45%, greater than that of tumor-bearing UT-B wild-type mice(P<0.01). We observed paraffin sections of tumor tissues from tumor-bearing UT-B knockout mice and wild-type control mice by HE staining. We found that the tumor cells were tightly arranged, with less necrosis and showed significant atypia; a small amount of lymphocytic infiltration occurred in the necrotic area as well. For the UT-B gene knockout mice, however, the tumor cells were disorderly arranged, had more necrosis and unobvious atypia; karyopyknosis was seen in cancer cells, and a large amount of lymphocytic infiltration occurred in the necrotic area as well.From the results mentioned above, our conclusions are as follow:knockout of UT-B gene leads to increased number of CD4+T cells and total T cells, which play great roles in immune reactions in periphery and spleen; knockout of UT-B gene could enhance immune function and promote tumor suppression; UT-B gene is closely related to the selective development and differentiation of organic lymphoid tissues towards T lymphocytes, and is closely related to occurrence and development of tumor as well.