SUMMARY:Diabetic nephropathy is a major complication of diabetes leading to thickening of the glomerular basement membrane, glomerular hypertrophy, mesangial expansion, and overt renal disease. The pathophysiologic mechanisms of diabetic nephropathy remain poorly understood. Nephrin is a recently found podocyte protein crucial for the interpodocyte slit membrane structure and maintenance of an intact filtration barrier. Here we have assessed the role of nephrin in two widely used animal models of diabetes, the streptozotocin model of the rat and the nonobese diabetic mouse. In both models, the expression levels of nephrin-specific mRNA as determined by real-time quantitative polymerase chain reaction increased up to two-fold during several weeks of follow-up. Immunohistochemical stainings revealed nephrin also more centrally within the glomerular tuft along with its preferential site in podocytes. Interestingly, as detected by immunoblotting, nephrin protein was also found in the urine of streptozotocin-induced rats. We conclude that nephrin is connected to the early changes of diabetic nephropathy and thus may contribute to the loss of glomerular filtration function. (Lab Invest 2001, 81:1185-1190.

Vascular adhesion protein-1 (VAP-1) is an endothelial molecule that possesses both adhesive and enzymatic properties in vitro. So far, however, elucidation of its in vivo function has suffered from the lack of function-blocking reagents that are suitable for use in animal models. In this work we produced monoclonal antibodies against murine VAP-1 and characterized them using in vitro binding assays. We then examined whether the antibodies could prevent leukocyte migration in in vivo inflammation models, including two acute models (peritonitis induced with proteose peptone and interleukin-1 and air pouch inflammation enhanced by CCL21) and one chronic model (autoimmune diabetes in nonobese diabetic mice). Antibodies 7-88 and 7-106 inhibited migration of granulocytes and monocytes in both acute models of inflammation. Strikingly, antibody 7-88 significantly prevented diabetes in a subset of nonobese diabetic mice. The results show for the first time that in mouse models of inflammation, VAP-1 mediates leukocyte trafficking to sites of inflammation and thus is a potential target for anti-inflammatory therapies.

Activation of an islet-specific immune response is an early yet essential step in autoimmune diabetes. The immune cells and antigen(s) involved in this early step and its anatomical site remain incompletely understood. To directly evaluate the site where islet-specific and diabetogenic lymphocytes are activated, we isolated lymphocytes from spleen and from pancreas-draining, gut-associated and subcutaneous lymph nodes of diabetic NOD mice and of young NOD mice, and transferred these into NOD scid/scid recipients devoid of endogenous islet-specific immune responses themselves. Although spleen lymphocytes from diabetic NOD mice induced diabetes more rapidly than lymphocytes from any other lymphoid tissue, spleen lymphocytes from young NOD donors were not superior to other lymphocytes from the same donors. At a donor-age of 6 weeks, the most-diabetogenic lymphocytes were found in pancreas-draining lymph node whereas gut-associated lymph nodes and the spleen were sources of intermediate diabetogenic activity. Lymphocytes from peripheral lymph nodes were only weakly diabetogenic at this age, and also remained the least efficient later. Surprisingly, lymphocytes isolated even from 3-week-old NOD mice had diabetogenic potential. However, such cells were almost exclusively found in gut-associated lymph nodes. This suggests that initial priming of diabetogenic cells takes place in the gut whereas pancreas-draining lymph nodes may serve as the site of amplification of the autoimmune response.

Ly-6C belongs to the Ly-6 family of glycosyl phosphatidylinositol-anchored surface glycoproteins and is expressed on a subset of mature CD8 ؉ T cells. Ly-6C ligation can mediate T cell activation and causes interleukin 2 secretion in cytolytic T cell clones. We characterize herein a new mAb 1G7.G10 against Ly-6C that recognizes an epitope involved in lymphocyte adhesion and in lymphocyte homing. Pretreatment of lymph node lymphocytes and of purified CD8 ؉ T cells (but not of lymphocytes depleted of CD8 ؉ T cells) with 1G7.G10 reduced their in vitro binding to lymph node high endothelial venules by 28% and 34%, respectively. This effect was bypassed by cross-linking Ly-6C molecules with 1G7.G10 and a second-step antibody. The in vivo homing of (donor) CD8؉ T lymphocytes to lymph nodes was reduced by Ly-6C blocking with 1G7.G10 (whole antibody) or with its fragments [F(ab) Ly-6 is a family of closely related murine glycoproteins that are mainly expressed by cells of the hematopoietic lineage. The Ly-6 locus encodes at least seven structurally related molecules that represent different serotypes (Ly-6A͞E, Ly-6B, Ly-6C, Ly-6D, Ly-6F, Ly-6G, and ThB) (1, 2). These Ly-6 specificities vary in their exact lymphoid and myeloid cell distribution and have, therefore, been studied extensively as hematopoietic differentiation antigens. Although the exact function of many of the Ly-6 molecules is still obscure, evidence suggests that these molecules participate in signaling steps during immune responses. (i) Ly-6A͞E can mediate T cell activation independently of other soluble or cell-mediated signals, and Ly-6C mediates at least costimulatory signals for T cell activation (3, 4).(ii) T cell Ly-6A͞E and Ly-6C can be up-regulated by interferons, including interferon ␥ (5), and by CD3 complex stimulation (6). The expression of Ly-6C on lymphocytes in Ly-6.1 mouse strains is restricted to a subset of peripheral CD8 ϩ T lymphocytes (Ϸ50% positive) (1), but also monocytes, macrophages, a subset of bone marrow mononuclear cells, and endothelial cells of small vessels express variable levels of Ly-6C (7).Lymphocyte recirculation and homing are a prerequisite for effective distribution of the whole repertoire of antigenresponsive lymphocytes within the whole body (8). A key event in lymphocyte homing is the interaction of the lymphocyte with vascular endothelial cells (ECs), which can be viewed as a stepwise process (9). Many of the molecules involved in the lymphocyte-EC interaction have been characterized in detail. The first step is mediated by lymphocyte (L-selectin, peripheral node homing receptor) and endothelial selectins (E-and P-selectin) (10) or, alternatively, by ␣4-integrins (␣4͞␤7, mucosal homing receptor, and ␣4͞␤1) (11) and is followed by firm adhesion of the lymphocyte to ECs mediated by ␤2-or, again, ␣4-integrins (12, 13). Before the integrin can mediate firm adhesion, it must be activated, which requires that the cell receives an appropriate signal. This signal can come from the binding of a membrane-bound ...

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