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

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

Interleukin-18 does not modulate the acute-phase response.

Contains fulltext : 47490.pdf (publisher's version ) (Open Access)IL-18 is a pro-inflammatory cytokine of the IL-1 family and it induces IL-1, TNF, and IL-6, all of which are endogenous pyrogens. The pyrogenic properties of recombinant IL-18 were studied in a rabbit model of fever. rIL-18 did not cause fever when injected intravenously into rabbits. Furthermore, the ability of rIL-18 to modulate other components of the acute-phase response was assessed. rIL-18 did not induce leukocytosis, or changes of circulating concentrations of lipoproteins and corticosterone in mice. In conclusion, rIL-18 is not able to induce a febrile response in rabbits and does not modulate the acute-phase response in mice

Anticardiolipin antibodies from patients with the antiphospholipid antibody syndrome recognize epitopes in both beta(2)-glycoprotein 1 and oxidized low-density lipoprotein.

BackgroundWe recently suggested that many anticardiolipin antibodies bind only to oxidized cardiolipin (OxCL) and/or to OxCL-beta(2)-glycoprotein 1 (beta(2)GP1) adducts but not to a "reduced" cardiolipin that is unable to undergo oxidation. To test this hypothesis, we investigated 24 sera, 4 protein A-purified IgG fractions, and 3 human monoclonal antibodies that were all isolated from patients with antiphospholipid antibody syndrome (APS); testing was also performed in 7 controls. Two monoclonal antibodies (IS3 and IS4) were selected for binding to CL and one was selected for binding to beta(2)GP1 (LJB8).Methods and resultsBy chemiluminescent immunoassay, all APS sera samples bound only to OxCL and not to reduced CL, and the binding was inhibited >95% by OxCL but not reduced CL. All purified IgG fractions bound to beta(2)GP1 but only when the beta(2)GP1 was plated on microtiter wells coated with OxCL. All 3 monoclonal antibodies bound only to OxCL. On Western blots, IS4 and LJB8 bound to beta(2)GP1 as well as to delipidated apoB of oxidized LDL but not to native apoB. IS3 also bound to oxidized apoB on Western blot. Covalent modification of beta(2)GP1 with oxidation products of CL made it more antigenic for APS serum samples, for purified IgG fractions, and for the monoclonal antibodies.ConclusionsThese data support the hypothesis that oxidation of CL is needed to generate epitopes for many anticardiolipin antibodies and that some of these epitopes are covalent adducts of OxCL with beta(2)GP1 or apoB

Sequence analyses of three immunoglobulin G anti-virus antibodies reveal their utilization of autoantibody-related immunoglobulin Vh genes, but not V lambda genes.

Accumulated sequence analyses of the antibody repertoire have revealed that most autoantibodies and developmentally regulated antibodies share a small set of germline Ig-variable region (V) genes. The findings have prompted speculation that certain autoantibodies are of developmental importance and may be instrumental in maintaining homeostasis of the adult antibody repertoire. In order to evaluate this hypothesis critically, it is first necessary to determine the V gene usage in human antibodies against foreign substances. Unfortunately, only a few such antibodies have had their heavy and light chains characterized. To rectify the situation, we adapted the anchored polymerase chain reaction to clone and analyze rapidly the expressed V genes for three anti-virus IgG antibodies. The results show that all three heavy chain V (Vh) genes are highly homologous to the known autoantibody-related Vh genes. In contrast, two light chain V (VL) genes of the V lambda 1 subgroup are similar to a non-autoantibody-related germline V lambda 1 gene. Taken together with the reported Vh and VL sequences of several antibodies against viruses and bacteria, the data show that many antipathogen antibodies may use the same small set of Vh genes that encode autoantibodies, but diverse VL genes that are distinct from autoantibody-related VL genes. Thus, only a small portion of the potentially functional germline Vh genes are used recurrently to generate most antibodies in a normal antibody repertoire, regardless of their reactivities with either self or non-self