ABSTRACT
Clonal anergy has been well recognized as an important mechanism of B cell immunologic tolerance. However, the properties of anergic B cells and especially their role in the development of autoimmune disease in susceptible animals have been controversial. Here we show that low-affinity anti-DNA anergic B cells populate the mature B-cell compartment in the mouse spleen in excessive numbers and display paradoxical behavior in response to a combined B-cell receptor/TLR9 activation. Surprisingly, B-cell anergy was maintained in aged NZB/NZW F1 mice that develop a systemic lupus erythematosus (SLE)-like autoimmune disease. In several parameters of anergy, such as calcium mobilization and antibody secretion, the lupus-prone mice appeared more anergic than their non-autoimmune counterparts. We conclude that low-affinity anergic B cells are unlikely to serve as precursors for the high-affinity autoreactive B cells that give rise to pathogenic anti-DNA auto-antibodies in SLE.
Subject(s)
Antibodies, Antinuclear/blood , Autoimmunity , B-Lymphocytes/immunology , Clonal Anergy , Lupus Erythematosus, Systemic/immunology , Spleen/immunology , Animals , Autoimmunity/genetics , B-Lymphocytes/metabolism , Calcium/metabolism , Cells, Cultured , Clonal Anergy/genetics , Disease Models, Animal , Lupus Erythematosus, Systemic/genetics , Lupus Erythematosus, Systemic/metabolism , Lymphocyte Activation , Mice , Mice, Inbred NZB , Mice, Transgenic , Receptors, Antigen, B-Cell/immunology , Spleen/metabolism , Toll-Like Receptor 9/immunologyABSTRACT
Recent work on B cell tolerance and autoimmunity has suggested the L chain allelic inclusion is a property of autoreactive B cells and is closely linked to receptor editing. Allelic inclusion could rescue autoreactive B cells from clonal deletion by reducing their effective BCR surface density. We have investigated this phenomenon in anti-DNA producing hybridomas, derived from different strains of Ig gene-targeted, lupus-prone NZB/NZW mice. Our results indicate that isotype and allelic exclusion was strictly maintained in most high- and low-affinity, edited and nonedited, anti-DNA transgenic B cells. However, a substantial fraction of the anti-DNA hybridomas expressed a very restricted set of nonproductively rearranged L chain mRNA, in addition to the productive anti-DNA L chain. The aberrant L chains could have a role in the selection and survival of autoreactive B cells in these autoimmune mice.
Subject(s)
Antibodies, Antinuclear/genetics , B-Lymphocytes/immunology , Immunoglobulin Heavy Chains/genetics , Lupus Erythematosus, Systemic/genetics , Lupus Erythematosus, Systemic/immunology , Receptors, Antigen, B-Cell/genetics , Amino Acid Sequence , Animals , Antibodies, Antinuclear/immunology , Autoimmunity , Base Sequence , Clonal Deletion , Flow Cytometry , Gene Knock-In Techniques , Gene Rearrangement, B-Lymphocyte/immunology , Hybridomas , Immunoglobulin Heavy Chains/immunology , Mice , Mice, Transgenic , Molecular Sequence Data , Receptors, Antigen, B-Cell/immunology , Reverse Transcriptase Polymerase Chain ReactionABSTRACT
CD22-deficient mice are characterized by B cell hyperactivity and autoimmunity. We have constructed knock-in CD22-/- mice, expressing an anti-DNA heavy (H) chain (D42), alone or combined with Vkappa1-Jkappa1 or Vkappa8-Jkappa5 light (L) chains. The Ig-targeted mice produced a lupus-like serology that was age- and sex-dependent. High-affinity IgG autoantibodies were largely dependent on the selection of B cells with a particular H/L combination, in which a non-transgenic, endogenous L chain was assembled by secondary rearrangements through the mechanism of receptor editing. Moreover, we present evidence that these secondary rearrangements are very prominent in splenic peripheral B cells. Since CD22 is primarily expressed on the surface of peripheral B cells, we propose a model for the development of a lupus-like autoimmune disease by a combination of peripheral receptor editing and abnormal B cell activation.
