Carol F. Webb, Ph.D.
Adjunct Professor, Departments of Microbiology & Immunology and Cell Biology, University of Oklahoma Health Sciences Center
Our immune system is made up of a number of special cells, proteins, tissues, and organs that protect the body from infectious organisms by recognizing and responding to those potentially harmful agents. Humoral immunity, or the part of the immune system that functions mainly in the blood, is mediated by antibodies (or immunoglobulins, which means immune proteins of the blood) that attach to foreign substances and flag the invading agent for destruction. These antibodies are produced by a type of white blood cell, called B-lymphocytes or B cells, and the genetic information required to make antibodies is specifically expressed only in these cells. In order for B cells to produce antibodies, they must first go through a process of development and maturation in the body. Then when mature B cells encounter a harmful agent, they can respond to signals inside the cell to express their antibody genes. The gene encoding an antibody is first copied or transcribed into a different type of molecule called mRNA. This process is called transcription and requires a complex set of interactions between a number of other proteins found in the nucleus of B cells. These enzymes and transcription factors provide the “on/off” signal to the cell, directing the cell to transcribe and express specific genes. Because only B cells express antibody genes, some of the protein factors are likely to be unique to B cells.
My laboratory performs basic research to understand the various stages of B cell development required for antibody production and the factors necessary for antibody gene transcription. Our recent studies have focused on a specific transcription factor, a protein that binds to DNA in B cells called Bright (B cell Regulator of ImmunoGlobulin Heavy chain Transcription), which we showed was involved in regulating antibody gene transcription.
Several years ago, we discovered that Bright associates with another protein that is important for normal B cell development, called Bruton’s tyrosine kinase, or Btk. Btk is critically important for B cell development as it has been identified as the defective enzyme in X-linked agammaglobulinemia (XLA), a disease that primarily affects boys and is characterized by an abnormally low antibody level. In XLA, a defect in the Btk gene results in the failure of early B cells to mature. The ultimate consequence of this block in B cell development is an almost complete absence of antibody production. XLA patients must be treated frequently with intravenous antibody in order to ward off infections that do not become severe in people with normal antibody levels. Although the specific genetic defect of XLA was identified in 1993, the underlying mechanisms that lead to the block in B cell development and low antibody levels remain unclear. Research in my laboratory is aimed at understanding these mechanisms.
Our laboratory uses a variety of approaches to investigate the function of the Bright transcription factor, including experimentation with isolated B cells and live mouse models. We found that the ability of Bright to provide the “on” signal to B cells and activate transcription of an antibody gene critically requires two additional proteins, Btk and another protein that interacts with Btk. These are the first findings to describe a direct link between the function of Btk and Bright in the expression of antibodies. Studies in genetically altered mice, or transgenic mice, are particularly useful since we can manipulate the production of specific proteins in these mice. By deleting, inhibiting, or even causing over-production of a protein such as Bright, we can learn more about how it functions. Using a transgenic mouse model, we discovered that mice that lack Bright function share similarities with XLA patients, including lower than normal antibody production in the blood. This is exciting and suggests that Bright function may also be important for antibody production in people. However, because most mouse models that have defects in Btk still differ in important ways from human patients with XLA, we are currently using new methods to study the role of Bright directly in human B cells.
In additional studies, our laboratory has discovered that maintaining proper levels of the Bright protein in B cells is important for preventing autoimmune symptoms where antibodies are inappropriately made against one’s own body. We generated transgenic mice that produce greater than normal amounts of Bright, and found that these mice develop autoimmune characteristics that resemble the autoimmune disease lupus seen in humans. Data from these mice have also helped to define the specific stages in B cell development that are important checkpoints for eliminating autoimmune antibodies that can react with one’s self. Studies to explore the effects of Bright over-expression on antibody production in human systems are also in progress.
Overall, the results of our studies are providing a better understanding of the mechanisms in B cells that control the production of antibodies in both autoimmune and immunodeficiency diseases. This information can then be used in the development of new drugs to treat these types of immune diseases.
A.B., Washington University, St. Louis, 1979
Ph.D., University of Alabama at Birmingham, 1985
Publications Committee, American Association of Immunologists, Section Editor, Journal of Immunology; Ad hoc Reviews: NIAID, NSF, Special Emphasis Panel (NIH), Gene, International Immunology, Molecular Immunology, Nucleic Acids Research, Journal of Biological Chemistry
American Association of Immunologists
American Society for Microbiology
American Association for the Advancement of Science
Joined OMRF Scientific Staff in 1990.
My long-term goal has been to develop a better understanding of the molecular mechanisms involved in B lymphocyte development and antibody production. A major focus of the lab has been to understand the function of the ARID (A+T interaction domain) family member ARID3a, or Bright (B cell regulator of immunoglobulin transcription), in this process. Several years ago we showed that Bright upregulates immunoglobulin heavy chain transcription as a member of a protein complex containing Bruton’s tyrosine kinase (Btk) and the ubiquitously expressed transcription factor TFII-I. Deficiencies in Btk result in immunodeficiency disease in both mice and humans and some of our work has focused on how inhibition of Bright function may cause immunodeficiency.
We first investigated Bright function by producing dominant negative forms of the protein. Bright binds to DNA as a dimer, so we generated and expressed mutants with defective DNA-binding activity that form sterile dimers with the endogenous protein resulting in inhibition of its function. Transgenic mice were also generated that express either dominant negative Bright, or constitutively over-express a wild type form of the protein specifically in B lymphocytes. Transgenic mice that expressed dominant negative Bright had reduced levels of serum IgM due to deficient function of a subpopulation of B lymphocytes. Because Bright interacts with Btk, and Btk deficiencies in man are much more severe than in mice, we extended our inhibition studies to human cells. Interestingly, myelopoiesis was blocked when ARID3a was over-expressed in early hematopoietic progenitors. Dominant negative ARID3a did not block myelopoiesis. We are now learning more about patterns of expression in human hematopoietic cells and continue to explore its roles in lympho-myeloid differentiation.
To our surprise, the transgenic mice that over-expressed wild type Bright were not immunodeficient, but rather, exhibited autoimmune symptoms. The Bright transgenic mice represent a unique model for studying how B cell tolerance is breached and should be informative about mechanisms responsible for early anti-nuclear antibody production.
Anti-nuclear antibody production is an early symptom in patients who develop lupus erythematosis. Therefore, in collaboration with Dr. Joan Merrill, we examined mononuclear blood samples from randomly selected lupus patients and discovered that more than half of those patients had measurable levels of ARID3a/Bright in their peripheral blood, while ARID3a was not detected in any of the age-matched control samples. These data suggest a link may exist between autoimmune disease and ARID3a expression in people. Further studies are in progress to determine the nature of this link.
Yusuf D, Butland SL, Swanson MI, Bolotin E, Ticoll A, Cheung WA, Zhang XY, Dickman CT, Fulton DL, Lim JS, Schnabl JM, Ramos OH, Vasseur-Cognet M, de Leeuw CN, Simpson EM, Ryffel GU, Lam EW, Kist R, Wilson MS, Marco-Ferreres R, Brosens JJ, Beccari LL, Bovolenta P, Benayoun BA, Monteiro LJ, Schwenen HD, Grontved L, Wederell E, Mandrup S, Veitia RA, Chakravarthy H, Hoodless PA, Mancarelli M, Torbett BE, Banham AH, Reddy SP, Cullum RL, Liedtke M, Tschan MP, Vaz M, Rizzino A, Zannini M, Frietze S, Farnham PJ, Eijkelenboom A, Brown PJ, Laperriere D, Leprince D, de CT, Prince KL, Putker M, Del PL, Camenisch G, Wenger RH, Mikula M, Rozendaal M, Mader S, Ostrowski J, Rhodes SJ, Van RC, Boulay G, Olechnowicz SW, Breslin MB, Lan MS, Nanan KK, Wegner M, Hou J, Mullen RD, Colvin SC, Noy PJ, Webb CF, Witek ME, Ferrell S, Daniel JM, Park J, Waldman SA, Peet DJ, Taggart M, Jayaraman PS, Karrich JJ, Blom B, Vesuna F, O'Geen H, Sun Y, Gronostajski RM, Woodcroft MW, Hough MR, Chen E, Europe-Finner N, Karolczak-Bayatti M, Bailey J, Hankinson O, Raman V, Lebrun DP, Biswal S, Harvey CJ, Debruyne JP, Hogenesch JB, Hevner RF, Heligon C, Luo XM, Blank MC, Millen KJ, Sharlin DS, Forrest D, Dahlman-Wright K, Zhao C, Mishima Y, Sinha S, Chakrabarti R, Portales-Casamar E, Sladek FM, Bradley PH, Wasserman WW. The Transcription Factor Encyclopedia. Genome Biol 13:R24, 2012. [Abstract]
Rose K, Long P, Shankar M, Ballard JD, Webb CF. Serum amyloid A protects murine macrophages from lethal toxin-mediated death. Cell Immunol 272:175-181, 2012. [Abstract]
Oldham AL, Miner CA, Wang HC, Webb CF. The transcription factor Bright plays a role in marginal zone B lymphocyte development and autoantibody production. Mol Immunol 49:367-379, 2011. [Abstract]
Webb CF, Bryant J, Popowski M, Allred L, Kim D, Harriss J, Schmidt C, Miner CA, Rose K, Cheng HL, Griffin C, Tucker PW. The ARID family transcription factor Bright is required for both hematopoietic stem cell and B lineage development. Mol Cell Biol 31:1041-1053, 2011. [Abstract]
An G, Miner CA, Nixon JC, Kincade PW, Bryant J, Tucker PW, Webb CF. Loss of Bright/ARID3a function promotes developmental plasticity. Stem Cells 28:1560-1567, 2010. [Abstract]
Schmidt C, Kim D, Ippolito GC, Naqvi HR, Probst L, Mathur S, Rosas-Acosta G, Wilson VG, Oldham AL, Poenie M, Webb CF, Tucker PW. Signalling of the BCR is regulated by a lipid rafts-localised transcription factor, Bright. EMBO J 28:711-724, 2009. [Abstract]
Nixon JC, Ferrell S, Miner C, Oldham AL, Hochgeschwender U, Webb CF. Transgenic mice expressing dominant-negative Bright exhibit defects in B1 B cells. J Immunol 181:6913-6922, 2008. [Abstract]
Shankar M, Nixon JC, Maier S, Workman J, Farris AD, Webb CF. Anti-nuclear antibody production and autoimmunity in transgenic mice that overexpress the transcription factor Bright. J Immunol 178:2996-3006, 2007. [Abstract]
Rajaiya J, Nixon JC, Ayers N, Desgranges ZP, Roy AL, Webb CF. Induction of immunoglobulin heavy-chain transcription through the transcription factor bright requires TFII-I. Mol Cell Biol 26:4758-4768, 2006. [Abstract]
Immunobiology and Cancer Research Program, MS 29
Oklahoma Medical Research Foundation
825 N.E. 13th Street
Oklahoma City, OK 73104
Phone: (405) 271-7999
Fax: (405) 271-2864