Does our current understanding of the molecular basis of immune tolerance predict new therapies for autoimmune disease?

Meta-analysis of the genetic association between PTPN22, CTLA-4 variants and risk of uveitis

BACKGROUND

Though the risk of PTPN22, CTLA-4 genetic variants with uveitis have been developed, the combined results still remain uncertain and controversial.

OBJECTIVES

To perform a meta-analysis to estimate the precise association of PTPN22 (rs2488457, rs2476601) and CTLA-4 (rs231775, rs5742909, rs4553808, and rs3087243) polymorphisms with uveitis susceptibility.

METHOD

Five electronic databases (PubMed, Embase, Web of Science, CBM, CNKI) were systematically searched for relevant literature up to July 20, 2021. All statistical analysis were evaluated by STATA 12.0 software and R programming language.

RESULTS

Our meta-results indicated that PTPN22 rs2488457 conferred positive susceptibility to uveitis (OR=1.18, 95%CI=1.02-1.38, p=0.029). In stratified analysis by ethnicity, rs2488457 C allele had a growing tendency towards uveitis in Asian region (OR=1.21, 95%CI=1.00-1.45, p=0.046). For CTLA-4 rs231775, subgroup analysis based on ethnicity manifested a negative association among uveitis individuals in Africa region (OR=0.25, 95%CI=0.19-0.33, p<0.001). For CTLA-4 rs4553808, subgroup analysis by disease type revealed that GG genotype was associated with an elevated risk of Behcet's disease (OR=3.22, 95%CI=1.05-9.90, p=0.042).

CONCLUSIONS

Our research revealed that PTPN22 rs2488457 conferred strong susceptibility to uveitis in general, especially in Asian region. CTLA-4 rs231775 conveyed protection against uveitis in African populations and CTLA-4 rs4553808 displayed an increased risk of Behcet's disease.

The danger hypothesis applied to idiosyncratic drug reactions

The danger hypothesis has had a profound effect on the way immunologists view the immune response. This hypothesis proposes that the major determinant of whether an immune response is mounted against some agent is determined by whether that agent causes some type of cell damage. Assuming that most idiosyncratic drug reactions (IDRs) are immune-mediated, this hypothesis also has the potential to explain many aspects of the mechanism of these adverse drug reactions. For example, most IDRs appear to be caused by chemical metabolites rather than the parent drug, but not all drugs that form reactive metabolites are associated with a significant incidence of IDRs. Therefore, using the danger hypothesis, one feature of a drug candidate that may predict whether it causes an IDR is whether the drug, or more likely its reactive metabolites, cause cell damage. Although the range of molecules that can act as danger signals is unknown, the most attractive candidates are high mobility group box 1 protein (HMGB1), heat shock proteins, and S100 proteins. These molecules act through the same receptors (toll-like receptors) as pathogen-associated molecules that stimulate the immune system. Therefore, other environmental factors such as infections or trauma might determine which patients would be at increased risk for IDRs. Although there are examples where this appears to be the case, in most cases there are no obvious environmental factors that determine IDR risk. In addition, in animal models of immune-mediated reactions, stimulation of toll-like receptors often does not increase the immune response, and depending on the timing, it can actually be protective. Therefore, there may be additional unknown control mechanisms that are involved. A better understanding of these fundamental immune mechanisms has the potential to have a significant impact on many areas of medicine.

Multiple functional targets of the immunoregulatory activity of galectin-1: Control of immune cell trafficking, dendritic cell physiology, and T-cell fate

In the postgenomic era, the study of the glycome-the whole repertoire of saccharides in cells and tissues-has enabled the association of unique glycan structures with specific physiological and pathological processes. The responsibility for deciphering this biological information belongs to endogenous glycan-binding proteins or lectins. Galectin-1, a prototypic member of a family of structurally related proteins, has demonstrated selective antiinflammatory and immunoregulatory effects either by controlling immune cell trafficking, "fine-tuning" dendritic cell physiology and regulating T-cell fate. These regulatory functions mediated by an endogenous glycan-binding protein may contribute to fulfill the needs for immune cell homeostasis, including preservation of fetomaternal tolerance and prevention of collateral damage as a result of microbial invasion or autoimmune pathology. We will discuss here the conceptual framework which led to the study of galectin-glycan lattices as a novel paradigm of immune cell communication in physiological and pathological processes and will highlight selected methods and experimental strategies which have contributed to the study of the immunoregulatory activities of this multifaceted glycan-binding protein both in in vitro and in vivo biological settings.

Conveying glycan information into T-cell homeostatic programs: a challenging role for galectin-1 in inflammatory and tumor microenvironments

The immune system has evolved sophisticated mechanisms composed of several checkpoints and fail-safe processes that enable it to orchestrate innate and adaptive immunity, while at the same time limiting aberrant or unfaithful T-cell function. These multiple regulatory pathways take place during the entire life-span of T cells including T-cell development, homing, activation, and differentiation. Galectin-1, an endogenous glycan-binding protein widely expressed at sites of inflammation and tumor growth, controls a diversity of immune cell processes, acting either extracellularly through specific binding to cell surface glycan structures or intracellularly through modulation of pathways that remain largely unexplored. In this review, we highlight the discoveries that have led to our current understanding of the role of galectin-1 in distinct immune cell process, particularly those associated with T-cell homeostasis. Also, we emphasize findings emerging from the study of experimental models of autoimmunity, chronic inflammation, fetomaternal tolerance, and tumor growth, which have provided fundamental insights into the critical role of galectin-1 and its specific saccharide ligands in immunoregulation. Challenges for the future will embrace the rational manipulation of galectin-1-glycan interactions both towards attenuating immune responses in autoimmune diseases, graft rejection, and recurrent fetal loss, while at the same overcoming immune tolerance in chronic infections and cancer.

Turning 'sweet' on immunity: galectin-glycan interactions in immune tolerance and inflammation

The function of deciphering the biological information encoded by the glycome, which is the entire repertoire of complex sugar structures expressed by cells and tissues, is assigned in part to endogenous glycan-binding proteins or lectins. Galectins, a family of animal lectins that bind N-acetyllactosamine-containing glycans, have many roles in diverse immune cell processes, including those relevant to pathogen recognition, shaping the course of adaptive immune responses and fine-tuning the inflammatory response. How do galectins translate glycan-encoded information into tolerogenic or inflammatory cell programmes? An improved understanding of the mechanisms underlying these functions will provide further opportunities for developing new therapies based on the immunoregulatory properties of this multifaceted protein family.