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Journal of Biomedicine and Biotechnology
Volume 2011 (2011), Article ID 275302, 9 pages
http://dx.doi.org/10.1155/2011/275302
Review Article

Role of PIR-B in Autoimmune Glomerulonephritis

Department of Experimental Immunology, Institute of Development, Aging and Cancer, Tohoku University, 4-1 Seiryo, Sendai 980-8575, Japan

Received 28 July 2010; Accepted 7 September 2010

Academic Editor: Monica Fedele

Copyright © 2011 Toshiyuki Takai et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

PIR-B, an inhibitory receptor expressed on murine B cells and myeloid cells, regulates humoral and cellular immune responses via its constitutive binding to the ligand, MHC class I molecules, on the same cells (cis) or on different cells (trans). Although it has been speculated that PIR-B is important for maintaining peripheral tolerance, PIR-B single deficiency does not cause overt autoimmune diseases. Recently, however, the combination of its deficiency with the Fas lpr mutation was found to result in augmented production of autoantibodies such as IgG rheumatoid factor and anti-DNA IgG, leading to glomerulonephritis in mice. Although the precise molecular mechanism for the overall scenario is unclear, PIR-B was found to suppress TLR9-mediated production of naturally autoreactive antibodies by innate B cells or B-1 cells by inhibiting the activation of Bruton's tyrosine kinase. Thus, PIR-B is an important regulator of innate immunity mediated by TLR9 in B-1 cells, which can otherwise provoke autoimmunity when overactivated.