One year in autoimmunity

Autoimmunity in 2016

The number of peer-reviewed articles published during the 2016 solar year and retrieved using the "autoimmunity" key word remained stable while gaining a minimal edge among the immunology articles. Nonetheless, the quality of the publications has been rising significantly and, importantly, acquisitions have become available through scientific journals dedicated to immunology or autoimmunity. Major discoveries have been made in the fields of systemic lupus erythematosus, rheumatoid arthritis, autoimmunity of the central nervous system, vasculitis, and seronegative spondyloarthrithritides. Selected examples include the role of IL17-related genes and long noncoding RNAs in systemic lupus erythematosus or the effects of anti-pentraxin 3 (PTX3) in the treatment of this paradigmatic autoimmune condition. In the case of rheumatoid arthritis, there have been reports of the role of induced regulatory T cells (iTregs) or fibrocytes and T cell interactions with exciting implications. The large number of studies dealing with neuroimmunology pointed to Th17 cells, CD56(bright) NK cells, and low-level TLR2 ligands as involved in multiple sclerosis, along with a high salt intake or the micriobiome-derived Lipid 654. Lastly, we focused on the rare vasculitides to which numerous studies were devoted and suggested that unsuspected cell populations, including monocytes, mucosal-associated invariant T cells, and innate lymphoid cells, may be crucial to ANCA-associated manifestations. This brief and arbitrary discussion of the findings published in 2016 is representative of a promising background for developments that will enormously impact the work of laboratory scientists and physicians at an exponential rate.

Ursodeoxycholic acid reduces CpG-induced IgM production in patients with primary biliary cirrhosis

AIM

Ursodeoxycholic acid (UDCA) treatment reduces IgM serum levels in patients with primary biliary cirrhosis (PBC) without affecting serum antimitochondrial antibody (AMA) titers. We previously reported that PBC-associated hyper-IgM is secondary to a disease-specific hyperproduction following bacterial stimulation by B cells.

METHODS

We isolated peripheral blood mononuclear cells (PBMC) from patients with PBC and controls and evaluated whether bacterial CpG challenge in the presence of UDCA at concentrations consistent with those achieved in treated patients led to changes in total IgM, IgG-AMA, and IgM-AMA production. Further, p65 phosphorylation and CD38 cell expression were analyzed as measures of activation of the NF-kB signaling pathway and B cell subsets, respectively.

RESULTS

UDCA significantly reduced CpG-induced total IgM and IgM-AMA production, but had no impact on IgG-AMA production. UDCA also significantly reduced the activation ofnaïve and IgM memory, but not IgG memory, B cells, as represented by CD38 expression levels. Further, p65 phosphorylation was significantly reduced in the presence of UDCA.

CONCLUSION

UDCA reduces total and IgM-AMA production in PBMC from patients with PBC by downregulating B cell activation and NF-kB signaling. These data ultimately suggest novel mechanisms of action for UDCA in chronic autoimmune cholestasis.

The immunological potential of galectin-1 and -3

A family of beta-galactosides-binding proteins, called galectins, have recently emerged as novel molecules with immunoregulatory functions. These proteins are expressed in both inflammatory and non-inflammatory cells including monocytes, macrophages, dendritic cells, mast cells, and B and T cells, giving a broad spectrum of involvement in the immune response. Galectins are uniquely capable of acting both intracellularly and extracellularly, affecting such processes as cell adhesion, signaling, proliferation, differentiation, and apoptosis. Different members of this family have been shown to modulate several pathological processes such as allergic reactions, autoimmunity, and tumor invasion. Therefore, understanding the role of galectins in achieving appropriate proliferative and effector responses to antigens will yield important insights to autoimmune diseases and delineate novel strategies for disease intervention.

Integrating immunity: the immunculus and self-reactivity

The most important theoretical contribution to autoimmunity was the clonal selection theory of Burnet. This thesis, including the unique terminology of the forbidden clone, laid the foundation for discussions and research regarding self-reactivity and remains the foundation for discussions of thymic education. There were, however, additional works which suggested that autoantibodies, coined natural autoantibodies, exist even in healthy individuals. The ontogenic appearance of the immune system was a series of events that were developed in evolution to recognize the biologic essence of complementary antigen recognition and elimination of foreign pathogens. Interestingly, microbial and host epitopes are often highly conserved in evolution and this homology has functional significance for both the microbe and the host. Further, while the immune system is a series of interconnecting pathways, in reality it is also composed of promiscuous and sometimes independent pathways. The interaction between antibodies and epitopes is determined not necessarily by a primary chemical structure, but more likely by the stereochemistry of the antigen. As such, we increasingly recognize a large repertoire of natural autoantibodies and the development of autoimmune disease requires more than an innocent bystander mimicry pathway, but rather expansion of lymphocytic populations that are either already naturally present, or derived from genetic/acquired defects in immune regulation. We suggest that discussion of loss of tolerance should not include focus on the classic terminology of peripheral versus central tolerance but must consider the integrative activity of the immune system and the balance between well-balanced self-reactivity and the processing of foreign antigens. These events, while primarily theoretical, provide a framework to understand the elements involved in genetic susceptibility to autoimmunity.