Exacerbation of autoimmune arthritis by copolymer-I through promoting type 1 immune response and autoantibody production

Impact of Glatiramer Acetate on B Cell-Mediated Pathogenesis of Multiple Sclerosis

Growing evidence indicates that B cells play a key role in the pathogenesis of multiple sclerosis (MS). B cells occupy distinct central nervous system (CNS) compartments in MS, including the cerebrospinal fluid and white matter lesions. Also, it is now known that, in addition to entering the CNS, B cells can circulate into the periphery via a functional lymphatic system. Data suggest that the role of B cells in MS mainly involves their in situ activation in demyelinating lesions, leading to altered pro- and anti-inflammatory cytokine secretion, and a highly effective antigen-presenting cell function, resulting in activation of memory or naïve T cells. Clinically, B cell-depleting agents show significant efficacy in MS. In addition, many disease-modifying therapies (DMTs) traditionally understood to target T cells are now known to influence B cell number and function. One of the earliest DMTs to be developed, glatiramer acetate (GA), has been shown to reduce the total frequency of B cells, plasmablasts, and memory B cells. It also appears to promote a shift toward reduced inflammation by increasing anti-inflammatory cytokine release and/or reducing pro-inflammatory cytokine release by B cells. In the authors' opinion, this may be mediated by cross-reactivity of B cell receptors for GA with antigen (possibly myelin basic protein) expressed in the MS lesion. More research is required to further characterize the role of B cells and their bidirectional trafficking in the pathogenesis of MS. This may uncover novel targets for MS treatments and facilitate the development of B cell biomarkers of drug response.

Effects of immunomodulators on the response induced by vaccines against autoimmune diseases

A promising treatment for T-cell-mediated autoimmune diseases is the induction of immune tolerance by modulating the immune response against self-antigens, an objective that may be achieved by vaccination. There are two main types of vaccines currently under development. The tolerogenic vaccines, composed of proteins formed by a cytokine fused to a self-antigen, which usually induce tolerance by eliminating the T-cells that are immune reactive against the self-antigen. The immunogenic vaccines, comprised of a self-antigen plus a sole Th2 adjuvant either free or conjugated, that alleviate autoimmunity by switching the immune response against the self-antigen, from a damaging pro-inflammatory Th1/Th17 to an anti-inflammatory Th2 immunity. Another type of vaccines is the DNA vaccines, where cells transiently express the self-antigen encoded by DNA, which induces a Th2 immunity. Actually, DNA vaccines can benefit from the presence of an adjuvant that elicits a systemic sole Th2 immunity to enhance the initially weak immune response characteristic of these vaccines. While in the tolerogenic vaccines, cytokines are the endogenous immunomodulators, in the immunogenic vaccines, the adjuvants are exogenous agents that elicit Th2 immunity with a production of anti-inflammatory cytokines and antibodies against the self-antigen. Because the commonly used Th2 adjuvant alum, fails to induce an effective immunity in the elderly population, it is unlikely that it would be widely used. Another Th2 adjuvant, the oil/water emulsions mixed with the antigen, while effective in vaccines against infectious agents, due to potential aldehydes in their formulation may be not suitable for autoimmune vaccines. A unique compound is glatiramer, which seems to be both a random polypeptide antigen and an immune modulator that biases the response to Th2 immunity. Its mechanism of action seems to implicate binding to MHC-II, which alters the outcome of T-cell signaling, leading to anergy. Glatiramer, while effective in the treatment of multiple sclerosis has not shown efficacy in other autoimmune diseases. An important new group of promising sole Th2 adjuvants are the fucosylated glycans, which by binding to DC-SIGN bias dendritic cells to Th2 immunity while inhibiting Th1/Th7 immunities. These glycans are similar to those produced by parasitic helminths to prevent inflammatory responses by mammalian hosts. A novel group of sole Th2 adjuvants are some plant-derived fucosylated triterpene glycosides, which share the immune modulatory properties from the fucosylated glycans. These glycosides have also an aldehyde group that delivers an alternative co-stimulatory signal to T-cells, averting the anergy associated with aging due to the loss of the CD28 receptor on T-cells. Hence, the development of vaccines to treat and/or prevent autoimmune conditions and some proteopathies, will significantly benefit from the availability of new sole Th2 adjuvants that while inducing an anti-inflammatory immunity, they do not abrogate pro-inflammatory Th1/Th17 immunities.

Glatiramer acetate in the treatment of multiple sclerosis: emerging concepts regarding its mechanism of action

Glatiramer acetate is a synthetic, random copolymer widely used as a first-line agent for the treatment of relapsing-remitting multiple sclerosis (MS). While earlier studies primarily attributed its clinical effect to a shift in the cytokine secretion of CD4+ T helper (T(h)) cells, growing evidence in MS and its animal model, experimental autoimmune encephalomyelitis (EAE), suggests that glatiramer acetate treatment is associated with a broader immunomodulatory effect on cells of both the innate and adaptive immune system. To date, glatiramer acetate-mediated modulation of antigen-presenting cells (APC) such as monocytes and dendritic cells, CD4+ T(h) cells, CD8+ T cells, Foxp3+ regulatory T cells and antibody production by plasma cells have been reported; in addition, most recent investigations indicate that glatiramer acetate treatment may also promote regulatory B-cell properties. Experimental evidence suggests that, among these diverse effects, a fostering interplay between anti-inflammatory T-cell populations and regulatory type II APC may be the central axis in glatiramer acetate-mediated immune modulation of CNS autoimmune disease. Besides altering inflammatory processes, glatiramer acetate could exert direct neuroprotective and/or neuroregenerative properties, which could be of relevance for the treatment of MS, but even more so for primarily neurodegenerative disorders, such as Alzheimer's or Parkinson's disease. In this review, we provide a comprehensive and critical overview of established and recent findings aiming to elucidate the complex mechanism of action of glatiramer acetate.

Glatiramer acetate treatment of multiple sclerosis: an immunological perspective

Glatiramer acetate (GA) has been used as an immunomodulatory agent for the treatment of relapsing-remitting multiple sclerosis (MS) in the United States since 1996. It is currently one of two first-line agents for use in the treatment of relapsing-remitting MS. GA was the first agent to be used in the treatment of MS that was developed using the animal model of MS called experimental autoimmune encephalomyelitis. In this commentary, we examine the development of GA as a treatment for MS and discuss its mechanism of action as suggested by recent studies using modern immunologic methods.

Recent insights into the mechanism of action of glatiramer acetate

Glatiramer acetate (GA, Copaxone®, co-polymer 1) is an immunomodulatory therapy approved in 1996 by the United States Food and Drug Administration for treatment of relapsing-remitting multiple sclerosis. GA has a good safety profile, moderate efficacy, and a unique mode of action. Recent evidence in an animal model of MS, experimental autoimmune encephalomyelitis (EAE), suggests that GA effects on NK cells and B cells may contribute to therapeutic efficacy. We review the mechanism of action of GA, with particular focus on recent data suggesting a role for regulatory B cells.

The absence of immunoglobulin D B cell receptor-mediated signals promotes the production of autoantibodies and exacerbates glomerulonephritis in murine lupus

Immunoglobulin (Ig)D is the major antigen receptor isotype co-expressed with IgM on the surface of most peripheral B cells in mice and humans. However, the biological role of IgD as B cell receptor (BCR) has remained unclear. Previous studies have indicated that IgD may play a role in B cell tolerance. To understand the role of IgD in B cell tolerance and autoimmunity, we have examined the development of autoimmune syndrome in lpr mice deficient for IgD. The present study showed that IgD deficiency did not alter lymphoproliferation and lymphocyte activation in lpr mice. The survival and proliferation of B cells were not affected by the absence of IgD, indicating that IgD BCR-mediated signals do not have an important role in negative selection of autoreactive B cell clones. Interestingly, compared to IgD-competent littermates, lpr mice with IgD deficiency had elevated autoantibody production, increased deposition of immune complex in the kidney and more severe nephritis. Accumulation of abnormal CD4(-) CD8(-) αβ(+) T cells was accelerated in IgD(-/-) lpr mice compared to lpr mice. These results suggest that IgD BCR-mediated signals may be involved in the differentiation of autoreactive B cells into plasma cells and abnormal T cell expansion.

Structure and function of interleukin-22 and other members of the interleukin-10 family

The IL-10 family of cytokines is comprised of IL-10, IL-19, IL-20, IL-22, IL-24, IL-26, and IFN-lambdas (IL-28A, IL-28B, and IL-29). The IL-10 family members bind to shared class II cytokine receptor chains that associate in various combinations in heterodimeric complexes. Upon interleukin/receptor complex formation, these proteins switch on the Jak/STAT pathway and elicit pleiotropic biological responses whose variety sharply contrasts with their structural similarities. IL-10 family members are involved in several human diseases and health conditions and hence their structural analyses may provide valuable information to design specific therapeutic strategies. In this review, we describe the human interleukin-10 family of cytokines, focusing on their structures and functions, with particular attention given to IL-22 and IL-10. We report on the recently published structures of IL-10 cytokine family members and their complexes with cognate transmembrane and soluble receptors as well as on interleukin physiology and physiopathology.

Glatiramer acetate increases IL-1 receptor antagonist but decreases T cell-induced IL-1beta in human monocytes and multiple sclerosis

Mechanisms of action as well as cellular targets of glatiramer acetate (GA) in multiple sclerosis (MS) are still not entirely understood. IL-1beta is present in CNS-infiltrating macrophages and microglial cells and is an important mediator of inflammation in experimental autoimmune encephalitis (EAE), the MS animal model. A natural inhibitor of IL-1beta, the secreted form of IL-1 receptor antagonist (sIL-1Ra) improves EAE disease course. In this study we examined the effects of GA on the IL-1 system. In vivo, GA treatment enhanced sIL-1Ra blood levels in both EAE mice and patients with MS, whereas IL-1beta levels remained undetectable. In vitro, GA per se induced the transcription and production of sIL-1Ra in isolated human monocytes. Furthermore, in T cell contact-activated monocytes, a mechanism relevant to chronic inflammation, GA strongly diminished the expression of IL-1beta and enhanced that of sIL-1Ra. This contrasts with the effect of GA in monocytes activated upon acute inflammatory conditions. Indeed, in LPS-activated monocytes, IL-1beta and sIL-1Ra production were increased in the presence of GA. These results demonstrate that, in chronic inflammatory conditions, GA enhances circulating sIL-1Ra levels and directly affects monocytes by triggering a bias toward a less inflammatory profile, increasing sIL-1Ra while diminishing IL-1beta production. This study sheds light on a mechanism that is likely to participate in the therapeutic effects of GA in MS.