Light chain editing in kappa-deficient animals: a potential mechanism of B cell tolerance.

During B lymphocyte development, antibody genes are assembled by DNA recombination. Successful cell surface expression of IgM promotes developmental progression. However, when antigen receptors bind autoantigen, development is blocked and ongoing antibody gene recombination occurs, which often alters antibody specificity in a process called receptor editing. We demonstrate here a significant role of developmental block and receptor editing in B cell receptor quality control. During development a functional, non-self-reactive receptor undergoes receptor editing if its expression is below a certain threshold. Doubling the receptor gene dose promotes development in the absence of autoantigen, but allows editing when autoantigen is present. Thus, both underexpressed and harmful B cell receptors can undergo correction by receptor editing.

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

B cell receptor expression level determines the fate of developing B lymphocytes: Receptor editing versus selection

Kouskoff

Lacaud

Pape

et al. 2000

“…Expression of Ig κ and λ L chain was determined by a sandwich ELISA using goat anti-mouse Ig κ and goat antimouse Ig λ antibody (Southern Biotechnology). Vκ use in 56R H-chain-containing hybrids was analyzed by PCR using primers listed in Table S3 as described previously (15,17,(44)(45)(46)(47)(48).…”

Section: Methodsmentioning

confidence: 99%

Apoptotic marginal zone deletion of anti-Sm/ribonucleoprotein B cells

Kishi

Higuchi

Phoon

et al. 2012

CD40L is excessively produced in both human and murine lupus and plays a role in lupus pathogenesis. To address how excess CD40L induces autoantibody production, we crossed CD40L-transgenic mice with the anti-DNA H-chain transgenic mouse lines 3H9 and 56R, well-characterized models for studying B-cell tolerance to nuclear antigens. Excess CD40L did not induce autoantibody production in 3H9 mice in which anergy maintains self-tolerance, nor did it perturb central tolerance, including deletion and receptor editing, of anti-DNA B cells in 56R mice. In contrast, CD40L/ 56R mice restored a large number of marginal zone (MZ) B cells reactive to Sm/ribonucleoprotein (RNP) and produced autoantibody, whereas these B cells were deleted by apoptosis in MZ of 56R mice. Thus, excess CD40L efficiently blocked tolerance of Sm/RNP-reactive MZ B cells, leading to production of anti-Sm/RNP antibody implicated in the pathogenesis of lupus. These results suggest that self-reactive B cells such as anti-Sm/RNP B cells, which somehow escape tolerance in the bone marrow and migrate to MZ, are tolerized by apoptotic deletion in MZ and that a break in this tolerance may play a role in the pathogenesis of lupus.peripheral tolerance | lupus-related autoantibody | marginal zone B cells M aintenance of B-cell tolerance occurs at various checkpoints throughout B-cell development and maturation and involves multiple mechanisms. Self-reactive immature B cells are subjected to central tolerance mechanisms in the bone marrow, including deletion by apoptosis (clonal deletion), functional inactivation (clonal anergy), or Ig V gene replacement (receptor editing) (1-4). B-cell tolerance can also occur after B cells leave the bone marrow and home to peripheral lymphoid organs. This peripheral tolerance involves mechanisms such as anergy, ignorance, and maturation arrest (5-7). Moreover, how tolerance is maintained in self-reactive B cells, which are anergized in bone marrow and migrate to the peripheral lymphoid tissues, has been extensively studied. These B cells are excluded from the follicle or marginal zone (MZ) and show reduced longevity (2, 8-10) attributable to increased dependence on B cell-activating factor belonging to the tumor necrosis factor family (BAFF) for survival (11, 12). However, it is not fully understood how peripheral tolerance mechanisms are broken in autoimmunity.B-cell self-tolerance has been addressed using antibodytransgenic (Tg) mice in which most of the B cells are reactive to a particular self-antigen. The anti-DNA H-chain Tg mice 3H9 and 56R are well-characterized models for studying B-cell tolerance to nuclear antigens (1, 10, 13-16), to which autoantibodies are characteristically produced in various autoimmune diseases including systemic lupus erythematosus (SLE). The 56R H chain was generated by introducing an arginine residue to the 3H9 VH region to increase affinity of the transgene-encoded antibodies for DNA. When paired with almost any of the mouse endogenous Ig L chains, both the 3H9 and the 56R H chains form an...

“…Shown for comparison are previously published data from hybridoma panels from 3H9.κ-/κ-, 56R.κ-/κ-, and nontg κ-/κ-mice (13; data from ref. 60, copyright 1994, Rockefeller University Press). κ-/κ-refers to homozygous κ-deficiency.…”

Section: Hybridomasmentioning

confidence: 99%

Alternative mechanisms of receptor editing in autoreactive B cells

Kalinina

Doyle-Cooper

Miksanek

et al. 2011

Pathogenic anti-DNA antibodies expressed in systemic lupus erythematosis bind DNA mainly through electrostatic interactions between the positively charged Arg residues of the antibody complementarity determining region (CDR) and the negatively charged phosphate groups of DNA. The importance of Arg in CDR3 for DNA binding has been shown in mice with transgenes coding for anti-DNA V H regions; there is also a close correlation between arginines in CDR3 of antibodies and DNA binding. Codons for Arg can readily be formed by V(D)J rearrangement; thereby, antibodies that bind DNA are part of the preimmune repertoire. Anti-DNAs in healthy mice are regulated by receptor editing, a mechanism that replaces κ light (L) chains compatible with DNA binding with κ L chains that harbor aspartic residues. This negatively charged amino acid is thought to neutralize Arg sites in the V H . Editing by replacement is allowed at the κ locus, because the rearranged VJ is nested between unrearranged Vs and Js. However, neither λ nor heavy (H) chain loci are organized so as to allow such second rearrangements. In this study, we analyze regulation of anti-DNA H chains in mice that lack the κ locus, κ-/κ-mice. These mice show that the endogenous preimmune repertoire does indeed include a high frequency of antibodies with Arg in their CDR3s (putative anti-DNAs) and they are associated mainly with the editor L chain λx. The editing mechanisms in the case of λ-expressing B cells include L chain allelic inclusion and V H replacement.autoimmunity | tolerance A nti-DNA antibodies bind DNA mainly through electrostatic interactions between the positively charged Arg (R) residues of the antibody complementarity determining regions (CDRs) and the negatively charged DNA phosphodiester backbone (1). Arg enrichment has been demonstrated in the protein sequences of anti-DNA antibody heavy (H) chains (2, 3). In addition, reverse mutagenesis of an H chain Arg to a germline amino acid weakened DNA binding, whereas forward mutagenesis with additional Arg residues enhanced DNA binding (1). The predominant occurrence of Arg residues in the V H -encoded CDRs of anti-DNA antibodies indicates a dominant role for V H in DNA binding, and the DNA specificity of these H chains persists when paired with a wide variety of light (L) chains (4-6). There are exceptional L chains (4 Vκ L chains of 95 functional Vκ genes and 1 Vλ L chain of 4 functional Vλ L chains) of the mouse that modify or veto the DNA-binding quality of 7,8). These editor L chains are characterized by a high content of aspartate, a negatively charged amino acid that efficiently neutralizes the positively charged Arg residues of anti-DNA H chains (4). B cells that express an anti-DNA V H with a noneditor L chain can undergo further L chain rearrangement. If the original L chain is replaced by an editor L chain, the B cell will be tolerized (4, 7). Similarly, MHC class I-reactive B cells (found in 3-83μ transgenic mice) that encounter autoantigen in the bone marrow continue rearrangement and change rece...