Detection of anti-cytokine antibodies and their clinical relevance

Abstract

Cytokines regulate many aspects of cell growth and differentiation and play pivotal roles in the orchestration of immune defence against invading pathogens. Though ‘self’ proteins, they are potentially immunogenic and can give rise to anti-cytokine autoantibodies (aCA). The main foci of the article are a critical summary of the various methodologies applied for detecting and measuring aCA and a broad review of studies of the occurrence, characterization and clinical relevance of aCA in normal healthy individuals, patients with autoimmune diseases or microbial infections and aCA in patients whose disease is treated with recombinant cytokine products. The need for technical and methodological improvement of assays, including validation and standardization, together with approaches to harmonize calculation and reporting of results is also discussed.

Keywords::

• anti-cytokine autoantibodies
• bioassays
• clinical relevance
• immunoassays
• neutralizing antibodies

Financial & competing interests disclosure

The authors have no relevant affiliations or financial conflict with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in this manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Cytokines are a diverse family of proteinaceous mediators of cellular activities. As proteins, they are capable of eliciting immune responses, particularly the development of autoantibodies in situations where immune tolerance to self-proteins is deficient.

• A wide range of immunochemical and biological methods is available to detect and quantify anticytokine autoantibodies (aCAs). Each method has both advantages and disadvantages. To be fit for purpose and effective, accurate and precise, they require validation regarding specificity, sensitivity, reproducibility and appropriate analytical and statistical approaches for the calculation and reporting of results. However, operational and analytical variations among laboratories conducting assay methods have generated widely varying results and inconsistencies in the reporting of aCA concentrations or titers.

• It is probable that aCA to some cytokines exists in a low proportion of the apparently normal healthy population, but currently, figures for their exact prevalence are to a large extent confounded by insensitive assays and unreliable data. It is possible that immune complexes between aCA and circulating cytokine compromise the capacity of assays to detect and measure aCA in some cases.

• High concentrations and neutralizing titers of aCA against interferons (IFNs) have been found in autoimmune diseases where central tolerance is defective, especially autoimmune polyglandular syndrome type 1 (APS-1) and thymoma-associated myasthenia gravis. The clinical relevance of anti-IFN autoantibodies has been difficult to ascertain, possibly due to redundancy in the IFN-system. T_H17 cell-produced cytokines, IL-17A, IL-17F and IL-22, have been commonly found in APS-1 patients. In the latter, such aCAs are highly correlated with the yeast infection chronic mucocutaneous candidiasis, an early diagnostic disease feature of APS-1.

• Recombinant cytokines used therapeutically to treat human diseases have induced aCA in variable numbers of patients. Products from the IFN family have been most studied. In patients developing neutralizing aCA, the beneficial activities of the therapeutic cytokine are abrogated and patients become treatment resistant. Switching patients to alternative cytokine products is not always possible, for example, for IFN-β in multiple sclerosis therapy where aCAs neutralize all forms of IFN-β. For effective and safe therapies and patient management, there is an overriding need to monitor patients being treated with recombinant cytokines for the development of aCA.

• There remains an urgent need to improve the performance of assays to detect and measure aCA. The wider availability of characterized aCA preparations, cell lines and reagents should aid this goal, but standardization of assay methods and harmonization of results analyses and reporting are also required. New technologies should be developed to reduce the time taken to perform assays and to reduce costs.