Functional and phenotypic characteristics of testicular macrophages in experimental autoimmune orchitis

Abstract

Testicular inflammation with compromised fertility can occur despite the fact that the testis is considered an immunoprivileged organ. Testicular macrophages have been described as cells with an immunosuppressor profile, thus contributing to the immunoprivilege of the testis. Experimental autoimmune orchitis (EAO) is a model of organ-specific autoimmunity and testicular inflammation. EAO is characterized by an interstitial inflammatory mononuclear cell infiltration, damage of the seminiferous tubules and germ cell apoptosis. Here we studied the phenotype and functions of testicular macrophages during the development of EAO. By stereological analysis, we detected an increased number of resident (ED2+) and non-resident (ED1+) macrophages in the testicular interstitium of rats with orchitis. We showed that this increase was mainly due to monocyte recruitment. The in vivo administration of liposomes containing clodronate in rats undergoing EAO led to a reduction in the number of testicular macrophages, which correlated with a decreased incidence and severity of the testicular damage and suggests a pathogenic role of macrophages in EAO. By immunohistochemistry and flow cytometry we detected an increased number of testicular macrophages expressing MHC class II, CD80 and CD86 costimulatory molecules in rats with orchitis. Also, testicular macrophages from rats with EAO showed a higher production of IFNgamma (ELISA). We conclude that testicular macrophages participate in EAO development, and the ED1+ macrophage subset is the main pathogenic subpopulation. They stimulate the immune response through the production of pro-inflammatory cytokines and antigen presentation and thus activation of T cells in the target organ.

Intratesticular Expression of mRNAs of Both Interferon γ and Tumor Necrosis Factor α is Significantly Increased in Experimental Autoimmune Orchitis in Mice

“…In immunohistochemical studies on testicular cytokines, it was revealed that testicular interstitial cells were positive for IFN-γ and TNF-α antibodies in EAO [7,19]. Enzyme-linked immunosorbent assays of testicular macrophages isolated from EAO-affected testes also demonstrated that these two cytokines were significantly secreted into the culture supernatant [8,9]. However, a real-time RT-PCR study of isolated dendritic cells obtained from TH+CFA+BP-EAOaffected testes did not show a significant change in TNF-α mRNA expression [20].…”

“…It has also been reported that the disease can be suppressed in vivo by the administration of anti-TNF-α antibodies but not anti-IFN-γ antibodies [6]. In rat EAO induced by immunization with TH+CFA+BP, it was shown that isolated testicular macrophages secreted both IFN-γ and TNF-α [7][8][9]. However, the intratesticular changes in IFN-γ and TNF-α mRNA expression at the organ level have not yet been investigated in any EAO model.…”

Testicular defense systems: immune privilege and innate immunity

“…By contrast, circulating macrophages significantly infiltrate the testis in orchitis and are detrimental to spermatogenesis. 40,41 Clinical observation revealed high macrophage numbers in the testis of patients with aspermatogenesis and infertility indicating a negative correlation between circulating macrophages and spermatogenesis. 42 Dendritic cells (DCs) exist in the testicular interstitial spaces and represent a minor population of the interstitial cells in the normal testis, reaching one-tenth of the numbers of macrophages.…”

Testosterone Replacement Effectively Inhibits the Development of Experimental Autoimmune Orchitis in Rats: Evidence for a Direct Role of Testosterone on Regulatory T Cell Expansion

“…Induced by immunization with testicular homogenate in adjuvant, EAO is characterized by the production of auto-antibodies against testicular Ags, elevated levels of proinflammatory cytokines (e.g., TNFa, IL-6) or chemokines (e.g., MCP-1), followed by the infiltration of leukocytes (mainly macrophages, dendritic cells, T lymphocytes) (12)(13)(14). An increase in the number of regulatory CD4 + CD25 + Foxp3 + T cells is also observed (15).…”