B-cell anergy is maintained in anti-DNA transgenic NZB/NZW mice.

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.

Autoreactive anti-DNA transgenic B cells in lupus-prone New Zealand black/New Zealand white mice show near perfect L chain allelic exclusion.

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.

Peripheral B cell receptor editing may promote the production of high-affinity autoantibodies in CD22-deficient mice.

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.

The effects of colchicine and hydroxychloroquine on the cyclo-oxygenases COX-1 and COX-2.

OBJECTIVE: The aim of this study was to test whether colchicine and hydroxychloroquine have an inhibitory effect on cyclo-oxygenases (COX). METHODS: Measurement of COX-1 and COX-2 activity was performed by using whole blood assay. Serum thromboxane (TXA) and plasma prostaglandin 2 (PGE2) levels were determined using a commercially available enzyme immunoassay kit. Celecoxib, etodolac, and nimesulide were also tested as controls. Since the study was intended to find a qualitative effect rather than a quantitative relationship between the drugs and the enzymes, we used higher concentrations than the therapeutic range. RESULTS: Colchicine did not have an inhibitory effect on cyclo-oxygenases. Hydroxychloroquine had a mild inhibitory effect in a relatively high concentration. As expected, celecoxib, etodolac, and nimesulide did have an inhibitory effect on the cyclo-oxygenases. CONCLUSIONS: Neither colchicine nor hydroxychloroquine exert their anti-inhibitory effect through inhibition of cyclo-oxygenases.

Autoimmune NZB/NZW F1 mice utilize B cell receptor editing for generating high-affinity anti-dsDNA autoantibodies from low-affinity precursors.

We have previously constructed knock-in (C57BL/6xBALB/c) F1 mice, each expressing an anti-DNA heavy (H) chain (D42), combined with one of three different light (L) chains, namely Vkappa1-Jkappa1, Vkappa4-Jkappa4 or Vkappa8-Jkappa5. All of these H/L chain combinations bind DNA with similar affinity and fine specificity. However, while mice carrying Vkappa1-Jkappa1-transgenic L chain were tolerized almost exclusively by L chain receptor editing, the mice expressing Vkappa8-Jkappa5 L chains utilized clonal anergy as their principal mechanism of B cell tolerance. Vkappa4-Jkappa4 targeted mice exhibited an intermediate phenotype. In the present study, these three H/L chain combinations were backcrossed onto the autoimmune NZB/NZW F1 mice. We find that the mechanism of clonal anergy is abrogated in these mice, but that receptor editing is maintained. Moreover, diseased NZB/NZW mice utilize L chain secondary rearrangements for the generation of high-affinity, anti-dsDNA-producing B cells from low-affinity precursors. The edited B cell clones are not deleted or anergized in the autoimmune animal; rather they are selected for activation, class-switching and affinity maturation by somatic mutation. These results suggest that B cell receptor editing plays an important role not only in tolerance induction, but also in generating high-affinity autoreactive B cells in autoimmune diseases.