What are autoimmune diseases?

The immune system protects the host from infectious materials, which requires recognition of self from non-self by antibodies. This is achieved with central and peripheral tolerance, in which a low level of autoreactivity is part of the normal function. However, the “breach of tolerance” is the term used when the immune system cannot distinguish self from nonself resulting in the activation of self-reactive T cells or B cells, or both, in the absence of infection leading to tissue destruction. The presence of high-affinity IgG autoantibodies causing tissue damage is the basis of autoimmune diseases.

Autoimmunity is classified as ‘physiological’ and ‘pathological’. Physiological autoimmunity is often transient with no clinical disease presentation. This includes natural autoantibodies, which help eliminate degraded antigens for homeostasis. In healthy individuals, there are still detectable levels of the common autoantibodies, antinuclear antibodies and rheumatoid factor, which increase with age. Pathological immunity occurs when the level of autoantibodies and self-reactive lymphocytes initiate the inflammatory response leading to a “breach of tolerance”, ultimately causing tissue damage.

What are the factors leading to autoimmune disease pathology?

Autoimmune diseases include more than 70 different disorders. Autoimmunity is theorized to occur due to genetic factors and environmental triggers. There is wide variability in the age of onset, affected tissues, and response to immunosuppressive treatments.

Autoimmune disease development due to genetic susceptibility is strongly linked to genetic variations in human leukocyte antigen (HLA) alleles which lead to a failure of self-tolerance and generation of active self-reactive lymphocytes, causing tissue injury. In contrast, environmental stimuli such as bacterial infections or tissue injury can cause activation of tissue antigen-presenting cells (APCs) followed by an influx of self-reactive lymphocytes, again leading to tissue damage.

Failure of B cell tolerance leads to the presence of autoantibodies. Autoantibodies are targeted against cell components such as nucleic acid and receptors. Autoantibodies and autoepitopes are becoming well-characterised for specific conditions. However, the presence of a specific autoantibody is not absolute confirmation of a clinical disease. Furthermore, some people can have autoantibodies present for a long pre-clinical period. However, their presence is a strong predictive factor.

Incidence and prevalence

Globally the incidence of autoimmune diseases is believed to be 3-5% of the population. Incidence and prevalence significantly vary amongst autoimmune diseases; variations in age, gender, ethnicity, and geographic location are also considerable. An example of geographic variability is multiple sclerosis, cases per 100,000 persons in tropical areas are below five. In contrast, in temperate areas per 100,000 persons, there are over 200. However, for almost all conditions, the prevalence significantly increases in first-degree relatives of a patient; this is even higher in monozygotic twins.

Genetic susceptibility

Women are significantly more predisposed to have an autoimmune disease. This bias is observed for systemic diseases such as Sjogren’s syndrome and organ-specific diseases, including multiple sclerosis. However, a few conditions see a significant male bias, such as ankylosing spondylitis and reactive arthritis. The basis for this is still the subject of research.

Mutations in key immunity-related genes have been linked to single monogenic diseases. A mutation in the autoimmune regulator (AIRE) gene affects negative selection in the thymus altering self-antigen presentation. This leads to autoimmune polyendocrinopathy syndrome type 1 (APS1), a multiple organ-specific autoimmune disease with a strikingly young age of onset, typically during childhood. However, monogenic autoimmune diseases are a rarity in the group. The majority of autoimmune diseases develop from multiple genetic factors.

There is clear evidence linking particular human leucocyte antigen (HLA) variants with specific autoimmune diseases. For example, psoriasis is strongly linked to the HLA alleles Cw*0602, Cw1203, and HCP5.  Genome-wide association studies (GWAS) have aimed to provide predictive tools about the major histocompatibility complex (MHC) for clinicians to use as prognostic tools for autoimmune diseases. However, they are yet to provide reliable results.

Alleles and loci have been identified as leading to a predisposition towards autoimmunity and familial linkage. However, epigenetic modifications can also cause a loss of tolerance. Aberrant methylation, acetylation, ubiquitination, SUMOylation, phosphorylation, and microRNA have all been implicated in specific autoimmune diseases. For example, microRNA signaling and DNA hypermethylation of insulin DNA, have been associated with type I diabetes.  Aberrant histone H3 and H4 global acetylation in active CD4 T cells are found in systemic lupus erythematosus. Epigenetic analyses can provide key insights into genetic susceptibility and environmental triggers interacting to lead to autoimmune pathology.

Environmental triggers

The lack of predictability of autoimmune disease development is partly due to environmental factors interacting with genetics. For example, the concordance of monozygotic twins ranges from 12 to 67%, implicating other external factors in pathology development. However, very few specific triggers have been confirmed to have a role in autoimmune diseases. Broadly, these environmental factors can include nutrition and the gut microbiota; lifestyle choices such as smoking; pharmaceuticals including drugs, hormones, xenobiotics, vaccines, and implants; and ultraviolet light.

Molecular mimicry is one of the leading mechanisms by which infectious or chemical agents can induce autoimmunity. Similar foreign and self-peptides lead to the activation of autoreactive T or B cells in a susceptible individual. There are numerous examples of molecular mimicry; however, this does not mean they are clinically significant.

Infectious agents and the resulting inflammatory response is the best characterized environmental factor for autoimmunity. For example, a genetically susceptible person who suffers a Streptococcus pyogenes infection is more likely to develop acute rheumatic fever. Theoretically, this is due to molecular mimicry between the bacterial M protein and human lysoganglioside leading to loss of tolerance and the development of cardiac reactive T cells. Around 30% of rheumatic fever patients develop rheumatic heart disease, so this mechanism could explain this prevalence in genetically susceptible individuals. 

Autoimmunity tissue destruction

Each and every autoimmune pathology is the result of disturbance to multistep effector pathways involving numerous cell types, resulting in a breach of tolerance forming self-destructive autoantibodies. The mechanism can be triggered by molecular mimicry, autoantigens and xenobiotics recognized by antigen-presenting cells. While autoantibodies are a significant feature of autoimmune diseases, they can also be found in cancer due to the massive tissue damage.

For some conditions, autoantibodies are detectable in healthy individuals and before symptoms appear. However, some are highly specific to a condition. A better-understood mechanism is autoantibodies binding cell surface antigen to label the cell for destruction. Antibodies lead to cell destruction generally by three methods; complement activation, macrophagic digestion, and antibody-dependent cell-mediated cytotoxicity (ADCC). The methods of cell destruction are discussed in depth in reviews.

Other autoantibodies react to membrane receptors leading to activation or blocking of selective pathways without causing cell destruction. Autoimmune thyroiditis (AT) Hashimoto’s thyroiditis sufferer’s autoantibodies recognize and bind cell membrane thyroid peroxidase. This leads to hypothyroidism due to TSH-like mimicry and the consequent inhibitory effect.

Tissue destruction can also occur when an antibody binds to a soluble antigen and forms an immune complex. Immune complexes are usually cleared by monocyte phagocytes as part of the normal immune response. However, if the amount of antigen and, thus, immune complexes overwhelms the clearance system, it can cause tissue damage. Deposition of immune complexes causes tissue damage such as glomerulonephritis, vasculitis and even arthritis; a mechanism seen in SLE.

Autoantibodies can also react with intracellular antigens. This is hypothesised to be via cross-reaction with membrane antigens and exposure of the antigens during apoptosis. SLE patients often have antibodies to bound histones and DNA molecules.

Extracellular proteins can be targets of autoantibodies such as prothrombin and annexin V. In lupus, autoantibodies recognise these phospholipid-binding plasma proteins causing a procoagulant effect.

For organ-specific autoimmune disease, autoantibodies bind to and cause injury to specific target organs, as is seen in myasthenia gravis. However, in systemic autoimmune diseases, autoantibodies react with free molecules and cell surface proteins to form pathogenic immune complexes. These can injure both tissues and organs through the engagement of FcγR activation of complement, as well as internalization and activation of Toll-like receptors. Immune complexes can lead to a positive feedback loop amplifying inflammatory responses. Activation of intracellular Toll-like receptors in plasmacytoid dendritic cells leads to the production of type I interferon, while engagement of intracellular Toll-like receptors on antigen-presenting cells stimulates cell activation and the production of other inflammatory cytokines.

How do we detect and diagnose autoimmune diseases?

Clinical features, serology, and histopathology are usually used to diagnose autoimmune diseases. Laboratory testing and imaging can initially identify signs of tissue destruction. Broadly, this can be via a complete blood count, detection of autoantibodies, and organ functionality analyses. Within each of these investigations, there are specific tests to detect aberrant immune reactivity. Some autoantibodies are highly specific to a condition. This provides the opportunity for the autoantibodies to be biomarkers for diagnosis and potential therapeutics.  For example, the thyroid functional test can be crucial to detect hormone levels for autoimmune thyroiditis. Following initial testing, there are more specific additional tests for confirmation, such as thyroperoxidase antibody detection for autoimmune thyroiditis.

Additional testing can be for genetic testing, T or B cell subset identification, cytokine levels, or at the organ level with tissue biopsy or imaging by MRI or CT scan.  Many of these tools will be used in conjunction to provide a definitive diagnosis, as no individual aspect is reliable and specific enough to be definitive. The development of proteomic, genomic, and metabolomics can offer far more sensitive and specific methodologies to understand autoimmunity and improve treatments in the future.

Autoimmune disease research tools

There are numerous proteins/genes that have been identified as having critical roles in immunity. Genetic mutations and dysregulation of protein function/levels can lead to autoimmune diseases. However, there is much that remains unclear.

Antibodies and Antigens for Diagnostics

Biosynth offers a range of antibodies and antigens for diagnostics through the Biosynth biologics team for new and emerging diseases, providing high-quality raw materials to the in-vitro diagnostic industry and research laboratories. We take pride in supplying critical raw materials to projects researching, diagnosing, and developing therapeutics for autoimmune diseases. We recognize the importance of further understanding the process of immune regulation; that is why we offer a wide range of custom and catalog products to research, detect, and manipulate the immune process. For the detection of key autoimmune markers, we have antibodies and proteins to known targets. These include:

• Myelin basic protein for multiple sclerosis
• amphiphysin for Stiff Person Syndrome (SPS)
• DPYSL5 for diaphanospondylodysostosis (DSD)
• TROVE2 and associated with Sjögren’s syndrome
• GARS associated with Charcot-Marie-Tooth disease
• JO1 and IARS associated with Polymyositis
• POLR3A associated with Leukodystrophy
• SSB and TRIM21 for Sjögren’s syndrome and Systemic Lupus Erythematosus (SLE)
• TPO associated with Hashimoto’s Thyroiditis

Detection and quantification assays

The accurate detection and quantification of serum antibodies is central to clinical diagnosis and classification of autoimmune diseases. ELISAs, indirect immunofluorescence and immunoblots have provided reliable, sensitive and specific results for samples. Biosynth offers various ELISA kits for screening samples, including dsDNA IgM, and IgG and IgA, as well as blocking peptides. Biosynth are the largest provider of bulk disease state plasma for controls in Europe. Use our research products search bar on our website to search for autoimmunity-related products for your project. We offer custom peptides and antibodies if you cannot find what you want in our research catalog. 

Biosynth has a catalog of polyclonal antisera to a range of human proteins. These cover a wide range of disease-state human plasma, including those involved in autoimmunity, thyroid function, as well as serum proteins and seroconversion panels.

We also have a large range of biospecimens providing positive controls for a number of diseases and antigens. This also includes a large range of purified human proteins from plasma urine or other fluids. Custom manufacture of antibodies and recombinant antigens occurs under ISO 13485:2016 conditions. Biosynth enables our customers to bring ground-breaking technology to the market faster, allowing cost-effective and efficient patient management at the point of impact.

However, these conventional diagnostics are relatively labour-intensive, time-consuming and notoriously difficult to standardize. Diagnostics have begun to move towards automation to address all of these issues. Automation can dramatically reduce human error, time, and strict standardization. At Biosynth, we understand the importance of antigen recognition for a specific autoantibody interaction with the epitope. Therefore, we offer epitope mapping for defining linear, conformational, and discontinuous epitopes to support antibody development and patent applications. Epitope mapping is an essential part of therapeutic antibody development. By providing a functional understanding of the critical residues involved, it can aid in the selection of antibodies, IP protection and FDA/EMA approval, and therefore in protecting the competitive interests of our customers.  Combining our scientists’ experience and expertise with our in-house developed peptide arrays and proprietary CLIPS™ technology provides us with a unique platform that allows us to define linear, conformational and discontinuous epitopes accurately and cost-effectively. In the majority of 2019 European patents that mentioned epitope mapping, we were the company of choice. For more information about how epitope mapping could move your project forward, please contact us.

Further to diagnostics is the choice of using either recombinant or native antigens in the detection of antibodies. For most, recombinant autoantigens are a convenient and reliable source for detection systems. Biosynth has a wide range of recombinant autoantigens for autoimmune diseases in its extensive catalog. Isolation of pure native antigens with sufficient yield and producibility is a significant problem for researchers. However, there are circumstances where the use of native autoantigens purified from mammalian tissues, or recombinant proteins produced in eukaryotic cells, are necessary. This is why Biosynth has native antigens available in its catalog but are always ready to begin custom manufacture of your antigen.

Treatments

Small molecules, peptides, and antibodies have all shown effectiveness on autoimmune diseases. Some treatments are specific to a condition or system while others are more broad spectrum, effecting the inflammatory response such as prednisolone; a non-specific drug that has been used to suppress inflammation and treat autoimmune diseases such as Crohn’s disease, and Inflammatory Bowel Disease (IBD).

Small molecules can be complex to generate but show significant opportunities to tackle autoimmune diseases. Poseltinib is a tyrosine kinase inhibitor that binds to the ATP-binding site of the receptor and blocks the binding of ATP, which inhibits protein synthesis. It shows promise for the treatment of cancer and autoimmune diseases. Lanraplenib is an experimental drug that has been shown to be effective in the treatment of autoimmune diseases. It is a small molecule that inhibits the activity of factor receptors and blocks the binding of cytokines and other inflammatory mediators to their receptors. Lanraplenib can be used for the treatment of chronic kidney disease, as well as systemic therapy for inflammatory diseases such as rheumatoid arthritis, psoriasis, and Crohn’s disease. Lanraplenib has also been found to have a favourable safety profile in clinical trials.

Peptides can provid targeted relief to sufferers. Hemopressin modulates the activity of the insulin receptor by binding to the carboxy terminal domain. This leads to increased insulin sensitivity and glucose uptake in peripheral tissues. Hemopressin has been shown to be effective against experimental models of autoimmune diseases, such as diabetes mellitus type 1 and multiple sclerosis. Bentazepam is an amide that has been shown to have a high absorption rate in humans and has been used as an absorption enhancer. Bentazepam also has therapeutic effects in autoimmune diseases, such as rheumatoid arthritis, systemic lupus erythematosus, and Crohn’s disease.

There are various antibodies already commercially available for the treatment of autoimmune conditions. Alemtuzumab is a monoclonal antibody against CD52, a protein present on the surface of mature lymphocytes but not on the stem cells from which these lymphocytes are derived. After treatment with alemtuzumab, these CD52-bearing lymphocytes are targeted for destruction. It is used for the treatment of multiple sclerosis. Rituximab is a glycosylated monoclonal antibody that binds to the CD20 cell surface protein, which is widely expressed on B-cells. Through the binding of rituximab’s Fc portion, the antibody-dependent cellular cytotoxicity pathway (ADCC) and the complement-dependent cytotoxicity (CDC) pathway are initiated, both leading to B-cell lysis. Rituximab is used in targeted therapy for multiple sclerosis. Sting agonist-4 is a monoclonal antibody that targets the molecule that is expressed in the target tissue. The subcutaneous tumor growth was inhibited by Sting agonist-4 in mice. This drug may also have immunomodulatory effects and can be used to treat microbial infections, neutrophil-associated inflammatory diseases, as well as cancer and inflammatory disease.

There is still significant research required to make a real difference to sufferers of autoimmune diseases. Biosynth has an unrivalled research product portfolio of over one million products and end-to-end manufacturing services, we are science-led and customer-focused to solve problems, taking pride in delivering products and projects that others cannot. Our expertise and capability runs across Complex Chemicals, Peptides and Key Biologics, all from one trusted partner. This makes Biosynth ideally placed to support novel discoveries all the way to clinical application.

About Biosynth

Securing Life Sciences Supply Chains – where Chemistry meets Biology, Products meets Services, and Innovation meets Quality, Biosynth is at the Edge of Innovation.  

With an unrivalled research product portfolio and end-to-end manufacturing services, we are science-led and customer-focused to solve problems and deliver key reagents at scale and quality. Our expertise and capability run across Complex Chemicals, Peptides, and Key Biologics, all from one trusted partner.   

Biosynth is an innovative life sciences reagents, custom synthesis and manufacturing services company. We are by scientists, for scientists, securing supply chains with consistent quality across the globe. We manufacture and source a vast range of chemical and biochemical products and take pride in delivering products that others cannot. We are experts in complex chemistry, peptides, and key biological raw materials. We provide a full range of products and services to support life science research and development, with more than half a million products in our research catalog and hundreds of complex manufacturing service projects. 

The trusted supplier, manufacturer and partner for the pharmaceutical, life science and diagnostic sectors, along with customers across food, agrochemistry and cosmetics, we have facilities across three continents and a rapid global distribution network. Our main chemical research and manufacturing laboratories are in Switzerland, the United Kingdom, Slovakia and China, with peptide production in the USA and the Netherlands. Enzyme projects are based in Austria, and biological IVD reagents are in Ireland.  Our R&D resources and production facilities are modern and versatile, allowing us to produce chemicals on the milligram to ton scale, and at ISO 9001 and GMP, with peptides at mg to multikilogram scale. 

References

Elkon (2008). Nature and functions of autoantibodies. Nature Clinical Practice. Rheumatology, 4(9)

Lleo (2010). Definition of human autoimmunity — Autoantibodies versus autoimmune disease. Autoimmunity Reviews, 9(5)

Meriggioli (2009). Autoimmune myasthenia gravis: Emerging clinical and biological heterogeneity. The Lancet Neurology, 8(5)

Tiniakou (2013). Sex-specific environmental influences on the development of autoimmune diseases. Clinical Immunology, 149(2)

Wang (2015). Human autoimmune diseases: A comprehensive update. Journal of Internal Medicine, 278(4)