- Meeting abstract
- Open access
- Published:
Evaluating the B-cell C3d:CR2 innate-adaptive immune interaction as a therapeutic target in lupus
Arthritis Research & Therapy volume 14, Article number: A38 (2012)
Background
B-cell targeted therapies are important strategies in human systemic lupus erythematosus (SLE). Previous studies have shown that B-cell complement receptor type 2 (CR2/CD21), along with its C3 activation fragment antigen-bound ligand designated C3d, play essential roles in the innate-adaptive immune interface and development of antibodies to foreign antigens. CR2 acts with CD19 to greatly amplify B-cell receptor signals. We hypothesize that a similar role is played by this receptor-ligand pair in the development of high-affinity IgG autoantibodies in patients with SLE. Prior gene-targeting studies have suggested, however, that CR2 expression may be needed to maintain tolerance. These studies are confounded, however, because not only is CR2 absent but due to murine-specific gene structures another receptor designated CR1 is also deleted at the same time. CR1 is a receptor for complement fragment C4b, whose deficiency in humans and murine models leads to lupus. In addition, a recent report of the first identified human CR2-deficient individual revealed a humoral immunodeficiency and not an autoimmune phenotype. Other recent studies have shown in MRL/lpr and (NZB×NZW)F1 mice that the use of soluble CR2 as a potential dominant negative inhibitor led to a substantial decrease in autoantibody titers.
Methods
To address our hypothesis, we developed novel mAbs that disrupt the CR2-C3d interface alone, without affecting the interactions of CR1 with C4b. We immunized C3-/- mice with recombinant human C3d, and Cr2-/- mice with recombinant murine CR2.
Results
The resultant human C3d-reactive mAbs inhibited C3d-CR2 binding, did not recognize intact C3/C3b, and cross-reacted with mouse C3d. Two anti-C3d mAbs, 3d29 and 3d8b, along with control mAb were pre-injected into mice before sheep red blood cell (SRBC) immunization. IgG1 responses to SRBC antigen were substantially decreased, consistent with the interruption in vivo of C3d binding to CR2. One resulting anti-CR2 mAb (4B2, IgG1), which directly blocks binding of C3d to CR2, was injected in wild-type mice and demonstrated no B-cell depletion but maintenance of blockade of CR2 on the B-cell surface for at least 1 month. SRBC immunization of mice pre-injected with mAb 4B2 revealed reduced anti-SRBC levels to levels found in immunized Cr2-/- mice. No anti-idiotype antibodies were detected.
Conclusion
We have developed unique tools to characterize in mouse models of human lupus the pathogenic roles of both the C3d ligand and CR2 components of the CR2-C3d interaction pair.
Author information
Authors and Affiliations
Rights and permissions
This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data.
About this article
Cite this article
Holers, V., Thurman, J., Hannan, J. et al. Evaluating the B-cell C3d:CR2 innate-adaptive immune interaction as a therapeutic target in lupus. Arthritis Res Ther 14 (Suppl 3), A38 (2012). https://doi.org/10.1186/ar3972
Published:
DOI: https://doi.org/10.1186/ar3972