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Genetic analysis of self-associating immunoglobulin G rheumatoid factors from two rheumatoid synovia implicates an antigen-driven response.

ABSTRACT: Although much has been learned about the molecular basis of immunoglobulin M (IgM) rheumatoid factors (RFs) in healthy individuals and in patients with mixed cryoglobulinemia and rheumatoid arthritis, little is known about the genetic origins of the potentially pathogenic IgG RFs in the inflamed rheumatoid synovia of patients. Recently, we generated from unmanipulated synovium B cells several hybridomas that secreted self-associating IgG RFs. To delineate the genetic origins of such potentially pathogenic RFs, we adapted the anchored polymerase chain reaction to rapidly clone and characterize the expressed Ig V genes for the L1 and the D1 IgG RFs. Then, we identified the germline counterparts of the expressed L1 IgG RF V genes. The results showed that the L1 heavy chain was encoded by a Vh gene that is expressed preferentially during early ontogenic development, and that is probably located within 240 kb upstream of the Jh locus. The overlap between this RF Vh gene and the restricted fetal antibody repertoire is reminiscent of the natural antibody-associated Vh genes, and suggests that at least part of the "potential pathogenic" IgG RFs in rheumatoid synovium may derive from the "physiological" natural antibody repertoire in a normal immune system. Indeed, the corresponding germline Vh gene for L1 encodes the heavy chain of an IgM RF found in a 19-wk-old fetal spleen. Furthermore, the comparisons of the expressed RF V genes and their germline counterparts reveal that the L1 heavy and light chain variable regions had, respectively, 16 and 7 somatic mutations, which resulted in eight and four amino acid changes. Strikingly, all eight mutations in the complementarity determining regions of the V gene-encoded regions were replacement changes, while only 6 of 11 mutations in the framework regions caused amino acid changes. Combined with L1's high binding affinity toward the Fc fragment, these results suggest strongly that the L1 IgG RF must have been driven by the Fc antigen.

SUBMITTER: Olee T

PROVIDER: S-EPMC2119156 | biostudies-other | 1992 Mar

REPOSITORIES: biostudies-other

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Genetic analysis of self-associating immunoglobulin G rheumatoid factors from two rheumatoid synovia implicates an antigen-driven response.

Olee T T Lu E W EW Huang D F DF Soto-Gil R W RW Deftos M M Kozin F F Carson D A DA Chen P P PP

The Journal of experimental medicine 19920301 3

Although much has been learned about the molecular basis of immunoglobulin M (IgM) rheumatoid factors (RFs) in healthy individuals and in patients with mixed cryoglobulinemia and rheumatoid arthritis, little is known about the genetic origins of the potentially pathogenic IgG RFs in the inflamed rheumatoid synovia of patients. Recently, we generated from unmanipulated synovium B cells several hybridomas that secreted self-associating IgG RFs. To delineate the genetic origins of such potentially ...[more]

PMID: 1740665

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Project description:BackgroundDepression is a disabling and highly prevalent condition where genetic and epigenetic, such as DNA methylation (DNAm), differences contribute to disease risk. DNA methylation is influenced by genetic variation but the association between polygenic risk of depression and DNA methylation is unknown.MethodsWe investigated the association between polygenic risk scores (PRS) for depression and DNAm by conducting a methylome-wide association study (MWAS) in Generation Scotland (N = 8898, mean age = 49.8 years) with replication in the Lothian Birth Cohorts of 1921 and 1936 and adults in the Avon Longitudinal Study of Parents and Children (ALSPAC) (Ncombined = 2049, mean age = 79.1, 69.6 and 47.2 years, respectively). We also conducted a replication MWAS in the ALSPAC children (N = 423, mean age = 17.1 years). Gene ontology analysis was conducted for the cytosine-guanine dinucleotide (CpG) probes significantly associated with depression PRS, followed by Mendelian randomisation (MR) analysis to infer the causal relationship between depression and DNAm.ResultsWidespread associations (NCpG = 71, pBonferroni < 0.05, p < 6.3 × 10-8) were found between PRS constructed using genetic risk variants for depression and DNAm in CpG probes that localised to genes involved in immune responses and neural development. The effect sizes for the significant associations were highly correlated between the discovery and replication samples in adults (r = 0.79) and in adolescents (r = 0.82). Gene Ontology analysis showed that significant CpG probes are enriched in immunological processes in the human leukocyte antigen system. Additional MWAS was conducted for each lead genetic risk variant. Over 47.9% of the independent genetic risk variants included in the PRS showed associations with DNAm in CpG probes located in both the same (cis) and distal (trans) locations to the genetic loci (pBonferroni < 0.045). Subsequent MR analysis showed that there are a greater number of causal effects found from DNAm to depression than vice versa (DNAm to depression: pFDR ranged from 0.024 to 7.45 × 10-30; depression to DNAm: pFDR ranged from 0.028 to 0.003).ConclusionsPRS for depression, especially those constructed from genome-wide significant genetic risk variants, showed methylome-wide differences associated with immune responses. Findings from MR analysis provided evidence for causal effect of DNAm to depression.

Project description:Immune homeostasis in tissues is achieved through a delicate balance between pathogenic T-cell responses directed at tissue-specific antigens and the ability of the tissue to inhibit these responses. The mechanisms by which tissues and the immune system communicate to establish and maintain immune homeostasis are currently unknown. Clinical evidence suggests that chronic or repeated exposure to self antigen within tissues leads to an attenuation of pathological autoimmune responses, possibly as a means to mitigate inflammatory damage and preserve function. Many human organ-specific autoimmune diseases are characterized by the initial presentation of the disease being the most severe, with subsequent flares being of lesser severity and duration. In fact, these diseases often spontaneously resolve, despite persistent tissue autoantigen expression. In the practice of antigen-specific immunotherapy, allergens or self antigens are repeatedly injected in the skin, with a diminution of the inflammatory response occurring after each successive exposure. Although these findings indicate that tissues acquire the ability to attenuate autoimmune reactions upon repeated responses to antigens, the mechanism by which this occurs is unknown. Here we show that upon expression of self antigen in a peripheral tissue, thymus-derived regulatory T cells (T(reg) cells) become activated, proliferate and differentiate into more potent suppressors, which mediate resolution of organ-specific autoimmunity in mice. After resolution of the inflammatory response, activated T(reg) cells are maintained in the target tissue and are primed to attenuate subsequent autoimmune reactions when antigen is re-expressed. Thus, T(reg) cells function to confer 'regulatory memory' to the target tissue. These findings provide a framework for understanding how T(reg) cells respond when exposed to self antigen in peripheral tissues and offer mechanistic insight into how tissues regulate autoimmunity.

Dataset Information

Genetic analysis of self-associating immunoglobulin G rheumatoid factors from two rheumatoid synovia implicates an antigen-driven response.

Publications

Genetic analysis of self-associating immunoglobulin G rheumatoid factors from two rheumatoid synovia implicates an antigen-driven response.

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