Stephen H. Clarke, Ph.D.
Stephen H. Clarke, Ph.D.
626 Mary Ellen Jones
Campus Box 7290
Chapel Hill, NC 27599-7290
919.966.3131
Research
B Lymphocytes in Health and Disease
The major interest of this laboratory is the differentiation and regulation of autoreactive B cells in health and disease. The molecular genetic process that determines B cell specificity inevitably results in B cells specific for self-antigens. Thus, mechanisms have evolved to eliminate these cells or render them non-functional. However, these mechanisms fail in individuals who develop autoimmune disease. Our long-range goal is to identify and understand the mechanisms that regulate autoreactive B cells and how they fail in disease. Such information is key to devise rational new therapeutic strategies for the treatment of autoimmune diseases.
Our research focuses on the regulation of B cells specific for the ribonucleoprotein antigen Sm, a target of the immune system in systemic lupus erythematosus (SLE). The presence of anti-Sm antibodies in serum is diagnostic of SLE and an indicator of more severe disease and poorer outcome. We have generated anti-Sm transgenic mice that produce a high frequency of anti-Sm B cells, making it possible to examine and follow the differentiation of these cells. We have identified multiple mechanisms of regulation. Some are eliminated by cell death, while others are rendered non-functional. Paradoxically, some anti-Sm B cells are positively selected for long-term survival and are functional. We seek to understand how these cells are regulated. Current evidence indicates that it is these positively selected and functional anti-Sm B cells that are activated in mouse SLE. Efforts are underway to understand how these cells are activated; the roles of T cells, dendritic cells, and the components of the complement system, all of which are strongly implicated in the etiology of SLE in humans and mice, are currently being examined.
We have also begun an analysis of how Epstein Barr virus (EBV) contributes to SLE. EBV is strongly associated with SLE in humans, but the mechanism is unknown. The current paradigm holds that molecular mimicry is responsible for anti-self B cell activation. Although this may occur, we think it is insufficient to explain the association, and argue that EBV infection of B cells alters the regulation of anti-self B cells. LMP2A encoded by the EBV genome, is known to affect B cell differentiation and we have recently demonstrated that LMP2A affects the regulation of anti-Sm B cells, allowing their activation and anti-Sm antibody production in mice. Efforts are underway to understand the underlying molecular and cellular mechanisms involved.
Finally, we have initiated studies in human SLE and determined that many patients with high titers of anti-Sm antibody in their serum also had high frequencies of anti-Sm B cells in their blood. These cells are predominantly memory B cells that have undergone somatic hypermutation. Interestingly, we identified abnormalities with their B cell receptor that may provide clues to how these cells are activated in human lupus. Current efforts are to understand the ability of these cells to be activated.
Publications
Wang, H., and S.H. Clarke. 2004. Regulation of B-cell development by antibody specificity. Curr Opin Immunol. 16(2):246-50. Review.
Wang, H., and S.H. Clarke. 2004. Positive selection focuses the VH12 B-cell repertoire towards a single B1 specificity with survival function. Immunol Rev. 197:51-9. Review.
Qian, Y., H. Wang, and S.H. Clarke. 2004. Impaired clearance of apoptotic cells induces the activation of autoreactive anti-Sm marginal zone and B-1 B cells. J Immunol. 172(1):625-35.
Wang, H., and S.H. Clarke. 2003. Evidence for a ligand-mediated positive selection signal in differentiation to a mature B cell. J Immunol. 171(12):6381-8.
Borrero, M., and S.H. Clarke. 2002. Low-affinity anti-Smith antigen B cells are regulated by anergy as opposed to developmental arrest or differentiation to B-1. J Immunol. 168(1):13-21.
Foscher, G.M., L.A. Solt, W.D. Hastings, K. Yang, R.M. Gerstein, B.S. Nikolajczyk, S.H. Clarke and T.L. Rothstein. 2001. Splenic and peritoneal B-1 cells differ in terms of transcriptional and proliferative features that separate peritoneal B-1 from splenic B-2 cells. Cell Immunol. 213(1):62-71.
M. Schultz, S.H. Clarke, L.B. Lefkowitz, R.J. Valuck, J. Lindenfeld, and K.A. Stringer. 2001. An institution-specific heparin titration nomogram: development, validation, and assessment of compliance. Pharmacotherapy. 21(10):1167-74.
Wang, H., Y. Qian, L.W. Arnold, S.K. McCray, and S.H. Clarke. 2001. A VH12 transgenic mouse exhibits defects in pre-B cell development and is unable to make IgM+ B cells. J Immunol. 167(3):1254-62.
Santulli-Marotto, S., Y. Qian, S. Ferguson, and S.H. Clarke. 2001. Anti-Sm B cell differentiation in Ig transgenic MRL/Mp-lpr/lpr mice: altered differentiation and an accelerated response. J Immunol. 166(8):5292-9.
Qian, Y., C. Santiago, M. Borrero, T.F. Tedder and S.H. Clarke. 2001. Lupus-specific antiribonucleoprotein B cell tolerance in nonautoimmune mice is maintained by differentiation to B-1 and governed by B cell receptor signaling thresholds. J Immunol. 166(4):2412-9.
Tatu, C., J. Ye, L.W. Arnold, and S.H. Clarke. 1999. Selection at multiple checkpoints focuses V(H)12 B cell differentiation toward a single B-1 cell specificity.
J Exp Med. 190(7):903-14.
