Th17 cells in inflammation and autoimmunity

Glycans as Vaccine Antigens and Adjuvants: Immunological Considerations

Carbohydrates can be found on the cell surface of nearly every cell ranging from bacteria to fungi right up to mammalian cells. Carbohydrates and their interactions with carbohydrate-binding proteins play crucial roles in multiple biological processes including immunity, homeostasis, cellular communication, cell migration, and the regulation of serum glycoprotein levels. In the last decades, the interest in exploiting the biological activity of glycans as vaccine components has considerably increased. On the one hand, carbohydrates display epitopes to generate protective antibodies against pathogen-derived cell wall structures and on the other hand, glycans have the potential to stimulate the immune system; thus they can act as potent vaccine adjuvants.An effective vaccine consists of two major components, the vaccine antigen and an adjuvant. The vaccine antigen is an original or modified part of the pathogen that causes the disease. The immune response triggered by vaccination should induce antigen-specific plasma cells secreting protective antibodies as well as the development of memory T and B cells. Carbohydrate structures on pathogens represent an important class of antigens that can activate B cells to produce protective anti-carbohydrate antibodies in adults. A major breakthrough in vaccine development was the design of conjugate vaccines that evoke protective antibody responses against encapsulated bacteria strains such as Haemophilus influenzae, Streptococcus pneumoniae, or Neisseria meningitidis in adults, but also in young children. The first part of this chapter focuses on immune responses triggered by carbohydrate-based vaccines. The second part of the chapter discusses the immunological mechanisms of carbohydrate-based adjuvants to increase the immunogenicity of vaccines.

The role of sex in uveitis and ocular inflammation

Uveitides can be due to non-infectious and infectious etiologies. It has been observed that there is a gender difference with a greater preponderance of non-infectious uveitis in women than in men. This review will describe both non-infectious and infectious uveitides and describes some of the current autoimmune mechanisms thought to be underlying the gender difference. It will specifically look at non-infectious uveitides with systemic involvement including juvenile idiopathic arthritis, spondyloarthopathies, sarcoidosis, Behçet’s disease, and Vogt-Koyanagi-Harada disease and at uveitides without systemic involvement including sympathetic ophthalmia, birdshot chorioretinitis, and the white dot syndromes. Infectious uveitides like acute retinal necrosis, progressive outer retinal necrosis, and cytomegalovirus mediated uveitis will be mentioned. Different uveitides with female- or male- predominance are presented and discussed.

Cytokine-modulating strategies and newer cytokine targets for arthritis therapy

Cytokines are the key mediators of inflammation in the course of autoimmune arthritis and other immune-mediated diseases. Uncontrolled production of the pro-inflammatory cytokines such as interferon-γ (IFN-γ), tumor necrosis factor α (TNFα), interleukin-6 (IL-6), and IL-17 can promote autoimmune pathology, whereas anti-inflammatory cytokines including IL-4, IL-10, and IL-27 can help control inflammation and tissue damage. The pro-inflammatory cytokines are the prime targets of the strategies to control rheumatoid arthritis (RA). For example, the neutralization of TNFα, either by engineered anti-cytokine antibodies or by soluble cytokine receptors as decoys, has proven successful in the treatment of RA. The activity of pro-inflammatory cytokines can also be downregulated either by using specific siRNA to inhibit the expression of a particular cytokine or by using small molecule inhibitors of cytokine signaling. Furthermore, the use of anti-inflammatory cytokines or cytokine antagonists delivered via gene therapy has proven to be an effective approach to regulate autoimmunity. Unexpectedly, under certain conditions, TNFα, IFN-γ, and few other cytokines can display anti-inflammatory activities. Increasing awareness of this phenomenon might help develop appropriate regimens to harness or avoid this effect. Furthermore, the relatively newer cytokines such as IL-32, IL-34 and IL-35 are being investigated for their potential role in the pathogenesis and treatment of arthritis.

Leukotrienes induce the migration of Th17 cells

Th17 cell trafficking in response to leukotriene signaling is poorly understood. Here we showed that Th17 cells express high levels of leukotriene B4 receptor 1 (LTB4R1) and cysteinyl leukotriene receptor 1 (CysLTR1). Th17 cells migrated under the guidance of leukotriene B4 and D4. The migration of Th17 cells was more efficient than that of Th1 and Th2 cells, and it was blocked by specific inhibitors of LTB4R1 or CysLTR1. Studies in an animal model of experimental autoimmune encephalomyelitis revealed that treatment with montelukast alleviated disease symptoms and inhibited the recruitment of Th17 cells to the central nervous system. Thus, leukotrienes may act as chemoattractants for Th17 cells.

Increased Th17 cells in flow cytometer-sorted CD45RO-positive memory CD4 T cells from patients with systemic lupus erythematosus

Objectives

Th17/IL-17 dysregulation is involved in human autoimmunity, and recent evidence suggests the character of long-lived differentiated memory cells in Th17. By directly measuring the peripheral blood mononuclear cells (PBMC), elevated circulating frequencies of Th17 cells have been reported in systemic lupus erythematosus (SLE) with inconsistent results regarding the correlation with disease activities. In this study, the association between circulating Th17 frequencies and disease activities or laboratory parameters was examined in flow cytometer-sorted CD45RO-positive memory CD4 T cells from SLE.

Methods

PBMC samples were obtained from 48 female lupus patients and another 48 age- and sex-matched healthy individuals. We examined frequencies of Th17 cells by sorting the purified CD4 T cells bearing the CD45RO marker, followed by intracellular IL-17A staining after in vitro activation. Frequencies of Th1 and T_Foxp3 cells were also measured by intracellular IFN-γ and Foxp3 staining, respectively. The SLE disease activity index (SLEDAI) and other laboratory parameters were further correlated with frequencies of different T cell subsets.

Results

In SLE, increased frequencies of Th17 cells were found with a positive correlation in SLEDAI. Higher frequencies of Th17 cells were found in lupus nephritis. There was a positive correlation between frequencies of Th17 cells and daily proteinuria amount.

Conclusions

By examining the sorted CD45RO-positive memory CD4 T cells, we confirm the dysregulation of Th17/IL-17 in SLE, implicating the potential to treat lupus patients with selective IL-17/IL-17R blockades.

Sodium chloride, SGK1, and Th17 activation

The incidence of autoimmune diseases in Western civilizations is increasing rapidly, suggesting an influence of environmental factors, such as diet. The pathogenesis of several of these autoimmune diseases is characterized by aberrant activation of T helper 17 (Th17) cells. Recent reports have shown that the differentiation of Th17 cells is sensitive to changes in local microenvironments, in particular salt (NaCl) concentrations, in a molecular mechanism centered around the serum- and glucocorticoid-inducible kinase 1 (SGK1). In this review, we summarize the recently disclosed mechanisms by which salt has been shown to affect SGK1 and, subsequently, Th17 activation.

The intestinal microbiota and microenvironment in liver

The intestinal microbiome plays a significant role in the development of autoimmune diseases, in particular, inflammatory bowel diseases. But the interplay between the intestinal tract and the liver may explain the increased association with autoimmune liver diseases and inflammatory bowel diseases. The gut-liver axis involves multiple inflammatory cell types and cytokines, chemokines and other molecules which lead to the destruction of normal liver architecture. Triggers for the initiation of these events are unclear, but appear to include multiple environmental factors, including pathogenic or even commensal microbial agents. The variation in the gut microbiome has been cited as a major factor in the pathogenesis of autoimmune liver disease and even other autoimmune diseases. The unique positioning of the liver at the juncture of the peripheral circulation and the portal circulation augments the interaction between naïve T cells and other hepatic cells and leads to the disruption in the development of tolerance to commensal bacteria and other environmental agents. Finally, the innate immune system and in particular toll-like receptors play a significant role in the pathogenesis of autoimmune liver disease.