Identification of immunodominant autoantigens in rat autoimmune orchitis

Using proteomics to identify targets of antiendothelial cell antibodies

Antiendothelial cell antibodies represent a heterogeneous group of antibodies directed against a variety of antigen determinants of endothelial cells. Antibodies reacting with endothelial structures have been detected in sera from patients with autoimmune vasculitis, both primary and secondary to systemic connective tissue diseases. It may interfere with several functions and, therefore, may be a pathophysiological relevance. The analysis of the antigens recognized by antiendothelial cell antibodies showed that the antibodies are directed against a heterogeneous family of both constitutive and nonconstitutive surface endothelial proteins. Proteomics is a field of science that evaluates a large number of proteins expressed from a given cell line or organism. The technology of proteomics has been used as a method for discovering the target protein specific to a particular disease by searching for the expression or modification of the protein. Recently, progress has been made in defining the target antigens of these antibodies and proteomic technologies is one of them. This review will focus on the proteomic technologies in searching autoantigens/autoantibodies associated with disease of the endothelium.

A sperm cytoskeletal protein TSA70 is a novel phosphorylated member of cenexin/odf2 family

Using post-vasectomy monoclonal antibody we recently identified a testis specific sperm auto-antigen called TSA70 which is post-meiotically expressed and plays a role in sperm motility and capacitation-acrosome reaction. In the present study, we report its cytoskeletal nature based on its resistance to various high ionic salt solutions. TSA70 is developmentally regulated and appears postpubertally. The two protein spots identified by 2D WB namely TSA1-pI=5.821, MW=77.050 and TSA3-pI=6.173, MW=75.519 showed sequence homology to Cenexin/odf2 indicating that two are isoforms of the same protein. The immunoreactivity of TSA70 with anti-Cenexin antibody substantiates its homology with Cenexin/odf2. In silico analysis revealed the presence of two leucine zippers in TSA70 and also predicted potential phosphorylation sites at serine, threonine, and tyrosine residues. The phosphorylated status of TSA70 was further confirmed by immunoblot analysis. The differential cellular expression suggests that TSA70 is a novel member of Cenexin/odf2 family that exhibits functional divergence.

Use of proteomics in analysis of autoimmune diseases

Autoimmune diseases are common by diseases characterized by disorders of immune responses and autoimmune impairment involving multiple tissues, organs and systems. The autoantigens (Ags)/autoantibodies (Abs) are not only hallmarks but also involved in pathogenesis of autoimmune diseases. In recent years, proteomics technologies have been used and demonstrated effective in searching new Ags/Abs as well as disease biomarkers in autoimmune diseases.

Induction of dominant tolerance using monoclonal antibodies

Monoclonal antibodies (MAb) have been shown to be effective in inducing immune tolerance in transplantation and autoimmunity. Several different MAb have tolerogenic properties and their effect has been studied in a range of experimental animal models and, in some cases, in clinical trials. The tolerant state seems to be maintained by CD4+ regulatory T cells (Treg), induced in the periphery, capable of suppressing other T cells specific for the same antigens or antigens presented by the same antigen presenting cells. Furthermore, following the initial induction of Treg cells under MAb treatment, Treg cells themselves can maintain the tolerant state in a dominant way in the absence of the therapeutic MAb or other immunosuppressive agents, and are able to recruit other T cells into the regulatory pool--a process named infectious tolerance.

The testis in immune privilege

The production, differentiation, and presence of male gametes represent inimitable challenges to the immune system, as they are unique to the body and appear long after the maturation of the immune system and formation of systemic self-tolerance. Known to protect germ cells and foreign tissue grafts from autoimmune attack, the 'immune privilege' of the testis was originally, and somewhat simplistically, attributed to the existence of the blood-testis barrier. Recent research has shown a previously unknown level of complexity with a multitude of factors, both physical and immunological, necessary for the establishment and maintenance of the immunotolerance in the testis. Besides the blood-testis barrier and a diminished capability of the large testicular resident macrophage population to mount an inflammatory response, it is the constitutive expression of anti-inflammatory cytokines in the testis by immune and particularly somatic cells, that represents an essential element for local immunosuppression. The role of androgens in testicular immune regulation has long been underestimated; yet, accumulating evidence now shows that they orchestrate the inhibition of proinflammatory cytokine expression and shift cytokine balance toward a tolerogenic environment. Furthermore, the role of the testicular dendritic cells in suppressing antigen-specific immunity and T-lymphocyte activation is discussed. Finally, the active role mast cells play in the induction and amplification of immune responses, both in infertile humans and in experimental models, highlights the importance of preventing mast cell activation to maintain the immune-privileged status of the testis.

Identification of a dendritic cell population in normal testis and in chronically inflamed testis of rats with autoimmune orchitis

Experimental autoimmune orchitis (EAO) in the rat is the primary chronic animal model for the investigation of one of the main causes of male infertility, viz., testicular inflammation. Dendritic cells (DC) are potent antigen-presenting cells that play a fundamental role in autoimmune disease. We investigated the number of DC in normal testis and examined whether DC infiltrated the testis during the development of EAO. EAO was induced by active immunization with testis homogenate and adjuvants in two strains of rat (Wistar and Sprague Dawley). The presence of DC in testis was determined, 50 and 80 days after the first immunization, by immunohistochemical staining with specific antibodies (OX-62 and CD11c), and then the total number of DC was measured by stereological analysis. Labeled cells were found only in the interstitial compartment and within granulomas of EAO animals. The number of DC in EAO testes increased compared with control rats in both strains, whereas the number of OX-62+ and CD11c+ cells in adjuvant controls remained unchanged compared with untreated rats. Interspecies variations in the quantity of DC were found, with the total number of DC per testis in untreated and adjuvant control Sprague-Dawley rats being about three times higher than that seen in Wistar rats. Moreover, the increase in DC numbers at 80 days was less prominent in EAO testes of Sprague-Dawley rats than in the Wistar strain in which EAO was more severe and showed a higher number of granulomae. Thus, we have identified the DC population in normal and chronically inflamed testis. The increase in DC observed in EAO suggests that, under inflammatory conditions, the modified action(s) of these cells is a factor in the induction of the autoimmune response in testis.

Development of testicular inflammation in the rat involves activation of proteinase-activated receptor-2

Mast cells are involved in early events crucial to inflammation and autoimmune disease. Recently, proteinase-activated receptor-2 (PAR(2)), a G-protein coupled receptor important to injury responses, was shown to be activated by mast cell tryptase. To investigate whether mast cells and PAR(2) are involved in the development and/or aggravation of testicular inflammation, we studied acute and chronic inflammatory models in the rat. In normal testes, PAR(2) was detected immunohistochemically in macrophages, in peritubular cells (PTCs) and in spermatid acrosomes. In experimentally induced autoimmune orchitis (EAO), PAR(2) was strongly upregulated in macrophages and peritubular-like cells, forming concentric layers around granulomas. Mast cells increased 10-fold in number, were more widely distributed throughout the interstitial tissue, and were partially degranulated. Isolated PTCs expressed functional PAR(2), responded to PAR(2) activation by phosphorylating extracellular signal-regulated kinases 1/2 (ERK1/2) and activating protein kinase c, and increased intracellular Ca(2+) concentrations as well as monocyte chemoattractant protein-1 (MCP-1), transforming growth factor beta(2) (TGFbeta(2)), and cyclooxygenase-2 (COX-2) mRNA expression. Expression of these inflammatory mediators, together with iNOS, also increased significantly in testes 50 days after EAO. In vivo, expression of cytokines and inflammatory mediators was upregulated after injection of recombinant tryptase (MCP-1, TGFbeta(2), and COX-2) and a specific PAR(2) peptide agonist (MCP-1, TGFbeta(2)) in the testis after 5 h. These results suggest that PAR(2) activation elicited on PTCs by mast cell tryptase contributes to acute testicular inflammation and that this pathogenetic mechanism may also play a role in autoimmune orchitis.