Autoantibody heritability in thyroiditis: IgG subclass contributions

Genome-wide association studies for immunoglobulin concentrations in colostrum and serum in Chinese Holstein

Background

The early death and health problems of calves caused substantial economic losses in the dairy industry. As the immune system of neonates has not been fully developed, the absorption of maternal immunoglobulin (Ig) from colostrum is essential in protecting newborn calves against common disease organisms in their early life. The overwhelming majority of Ig in bovine whey is transported from the serum. Therefore, Ig concentration in the colostrum and serum of dairy cows are critical traits when estimating the potential disease resistance of its offspring.

Results

Colostrum, blood, and hair follicle samples were collected from 588 Chinese Holstein cows within 24 h after calving. The concentration of total IgG, IgG1, IgG2, IgA and IgM in both colostrum and serum were detected via ELISA methods. With GCTA software, genome-wide association studies (GWASs) were performed with 91,620 SNPs genotyped by GeneSeek 150 K (140,668 SNPs) chips. As a result, 1, 5, 1 and 29 significant SNPs were detected associated with the concentrations of colostrum IgG1, IgG2, IgA IgM, and serum IgG2 at the genome-wide level (P < 3.08E–6); 11, 2, 13, 2, 12, 8, 2, 27, 1 and 4 SNPs were found significantly associated with total IgG, IgG1, IgG2, IgA and IgM in colostrum and serum at the suggestive level (P < 6.15E–5). Such SNPs located in or proximate to (±1 Mb) 423 genes, which were functionally implicated in biological processes and pathways, such as immune response, B cell activation, inflammatory response and NF-kappaB signaling pathways. By combining the biological functions and the known QTL data for immune traits in bovine, 14 promising candidate functional genes were identified for immunoglobulin concentrations in colostrum and serum in dairy cattle, they were FGFR4, FGFR2, NCF1, IKBKG, SORBS3, IGHV1S18, KIT, PTGS2, BAX, GRB2, TAOK1, ICAM1, TGFB1 and RAC3.

Conclusions

In this study, we identified 14 candidate genes related to concentrations of immunoglobulins in colostrum and serum in dairy cattle by performing GWASs. Our findings provide a groundwork for unraveling the key genes and causal mutations affecting immunoglobulin concentrations in colostrum and important information for genetic improvement of such traits in dairy cattle.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-08250-5.

Identification of IgG3-specific epitope that remedies problem in diagnostic IgG subclass determination due to human genetic variation

There are four subtypes of human IgG with different effector functions. Quantifying the relative amount of each IgG subtype is important for laboratory diagnosis in multiple settings. However, in an evolving landscape of the appreciation of human variability and the need for precision/personalised laboratory diagnosis, it has also been shown that there are numerous natural variants of IgG subtypes, with at least 29 having been described. It has recently been reported that commercially available polyclonal antisera to IgG3 cross react with variants of other IgG subtypes, while available monoclonal anti-IgG3 have a blind-spot for the IgG3-04 variant. Herein, we report that IgG3-04 contains an epitope in common with all known IgG3 variants and absent in other subtypes. A novel monoclonal anti-IgG3 is described that is specific to IgG3 but without any blind-spots for known IgG3 variants, providing a remedy to the problem of genetic variability of IgG3.

Errors in data interpretation from genetic variation of human analytes

In recent years, the extent of our vulnerability to misinterpretation due to poorly characterized reagents has become an issue of great concern. Antibody reagents have been identified as a major source of error, contributing to the "reproducibility crisis." In the current report, we define an additional dimension of the crisis; in particular, we define variation of the targets being analyzed. We report that natural variation in the immunoglobulin "constant" region alters the reactivity with commonly used subtype-specific anti-IgG reagents, resulting in cross-reactivity of polyclonal regents with inappropriate targets and blind spots of monoclonal reagents for desired targets. This raises the practical concern that numerous studies characterizing IgG subtypes in human disease may contain errors due to such previously unappreciated defects. These studies also focus attention on the broader concern that genetic variation may affect the performance of any laboratory or research test that uses antibodies for detection.

Thyroglobulin autoantibodies switch to immunoglobulin (Ig)G1 and IgG3 subclasses and preserve their restricted epitope pattern after 131I treatment for Graves' hyperthyroidism: the activity of autoimmune disease influences subclass distribution but not epitope pattern of autoantibodies

The subclass distribution of thyroglobulin autoantibodies (TgAb) is debated, whereas their epitope pattern is restricted. Radioidine ((131)I) treatment for Graves' disease (GD) induces a rise in TgAb levels, but it is unknown whether it modifies subclass distribution and epitope pattern of TgAb as well. We collected sera from GD patients before (131) I treatment and 3 and 6 months thereafter. We measured total TgAb, TgAb light chains and TgAb subclasses by enzyme-linked immunosorbent assay (ELISA) in 25 patients. We characterized the TgAb epitope pattern in 30 patients by inhibiting their binding to (125-) (I) Tg by a pool of four TgAb-Fab (recognizing Tg epitope regions A, B, C and D) and to Tg in ELISA by each TgAb-Fab. Total TgAb immunoglobulin (Ig)G rose significantly (P = 0.024). TgAb κ chains did not change (P = 0.052), whereas TgAb λ chains increased significantly (P = 0.001) and persistently. We observed a significant rise in IgG1 and IgG3 levels after (131)I (P = 0.008 and P = 0.006, respectively), while IgG2 and IgG4 levels did not change. The rise of IgG1 was persistent, that of IgG3 transient. The levels of inhibition of TgAb binding to Tg by the TgAb-Fab pool were comparable. A slight, non-significant reduction of the inhibition by the immune-dominant TgAb-Fab A was observed 3 and 6 months after (131)I. We conclude that (131)I treatment for GD increases the levels of the complement-activating IgG1 and IgG3 subclasses and does not influence significantly the epitope pattern of TgAb. In autoimmune thyroid disease subclass distribution of autoantibodies is dynamic in spite of a stable epitope pattern.

Heritability analysis of IgG4 antibodies in autoimmune thyroid disease

A study of IgG4 autoantibody levels in juvenile thyroid disease patients showed evidence of heritability using the ROMP screening method. These levels increased with time despite the fact that total IgG antibody decreased with time. Evidence of heritability was demonstrated only in patients with high titers of autoantibodies to both thyroglobulin (Tg) and thyroperoxidase (TPO) unlike family members who may show high titers of one or the other and be asymptomatic at the time of sampling. Since high and low IgG4 levels give different heritability plots, these findings may represent a more severe fibrotic form of thyroiditis with a distinct genetic background. Hence a simple predictive approach is offered by this screening tool for the disease in patients and family members which may be helpful in the future to identify IgG4-related thyroiditis early in the course of disease without the requirement for biopsy.

The long-term marriage between autoimmunity and internal medicine: a homage to Manuel Carlos Dias

Our understanding of autoimmune diseases results from the perfect combination of basic and clinical scientific research, and the figure that is closest to the proposed autoimmunology specialist is certainly the internist. The role of B cells in rheumatoid arthritis, the immunological mechanisms to fibrosis or to tissue specific damage, the classification of Bechet's syndrome, the clinical outcomes of antiphospholid syndrome, and new biomarkers for vascular complications in systemic sclerosis constitute, among others, are ideal examples of this combination. For these reason, this issue includes comprehensive reviews in all these areas and is dedicated to Dr. Manuel Carlos Dias and his career in the perfectioning and teaching of the clinical skills necessary to manage autoimmune disease. We are convinced that these discussions are likely of interest to basic scientists and clinicians alike for the proposed translational applications.

Autoimmunity in 2011

The mechanisms leading to the onset and perpetuation of systemic and tissue-specific autoimmune diseases are complex, and numerous hypotheses have been proposed or confirmed over the past 12 months. It is particularly of note that the number of articles published during 2011 in the major immunology and autoimmunity journals increased by 3 % compared to the previous year. The present article is dedicated to a brief review of the reported data and, albeit not comprehensive of all articles, is aimed at identifying common and future themes. First, clinical researchers were particularly dedicated to defining refractory forms of diseases and to discuss the use and switch of therapeutic monoclonal antibodies in everyday practice. Second, following the plethora of genome-wide association studies reported in most multifactorial diseases, it became clear that genomics cannot fully explain the individual susceptibility and additional environmental or epigenetic factors are necessary. Both these components were widely investigated, both in organ-specific (i.e., type 1 diabetes) and systemic (i.e., systemic lupus erythematosus) diseases. Third, a large number of 2011 works published in the autoimmunity area are dedicated to dissect pathogenetic mechanisms of tolerance breakdown in general or in specific conditions. While our understanding of T regulatory and Th17 cells has significantly increased in 2011, it is of note that most of the proposed lines of evidence identify potential targets for future treatments and should not be overlooked.