D. Nemazee, A. Gavin, C. Huber, D. Aït-Azzouzene, T. Ota, Patrick Skög, Min Lim, José Luis Vela, and Bao Duong
The main goal of our research is to understand how lymphocytes distinguish between self and nonself antigens. Because antigen receptors on lymphocytes are generated through an essentially random process, the generation of self-reactive cells most likely is a frequent occurrence. Regulation of such autoreactive specificities may be important to prevent autoimmune disease and to ensure efficient response to foreign microbes.
The development of B lymphocytes is a multistep process punctuated by the somatic generation of antibody heavy- and light-chain genes through DNA recombination, which is catalyzed by the recombinase activator gene-1 and recombinase activator gene-2 products. Because the V(D)J recombination is imperfect and error prone, pre-B and B cells are endowed with sensing mechanisms to detect protein expression of heavy chains and assembled heavy and light chains (i.e., intact surface IgM). A major function of the expression of immunoglobulin in immature B cells is signaling to downregulate recombinase activity and to stimulate developmental progression. Newly formed B-cell receptors are also screened for autoreactivity. These quality control mechanisms rely on signaling by antigen receptors.
Previously, we showed that B cells with autoreactive receptors do not downregulate recombination because of excessive signaling through the antigen receptor, resulting in "receptor editing," a process in which previously expressed genes for antibody light chains are inactivated and are replaced by secondary DNA recombination. More recent data indicated that editing can also play an important role in inactivating and replacing receptor genes that are underexpressed at the protein level. In this situation, subnormal expression of unligated surface immunoglobulin does not provide a needed signal. These results suggest that quality control of newly formed B lymphocytes is surprisingly stringent and that through recombinase regulation, B cells are often able to "repair" unacceptable light-chain genes by replacing the unacceptable genes with new genes. Because of the apparent efficiency of the editing process, we suspect that we have uncovered a major cellular "proofreading" pathway.
Current studies aim to determine the signaling pathways involved in translating a B cell receptor signal to the recombinase machinery and in determining the immunological consequences of defects in receptor editing. Mice genetically deficient in editing are being developed. These studies may shed light on the origins of autoimmune diseases that involve autoantibody production.
Because receptor editing is associated with a developmental block, we are using DNA array analysis and other screening methods to look more closely at changes in gene expression during and after receptor editing. A relatively small fraction of genes is differentially expressed, including a handful of previously uncharacterized mRNAs, which we are analyzing further.
In other studies, we focused on the cues that mature B cells use to distinguish self from nonself. Fully mature recirculating B cells can be rapidly inactivated and induced to apoptosis when confronted with tissue antigen, whereas the same cells are able to respond to antigens expressed by microbes. We are investigating both the death pathway involved in self-tolerance and the nature of the signals that prevent use of this pathway in responses to nonself antigens. The ability of B cells to distinguish self from nonself in this setting is independent of T lymphocytes and instead most likely involves a novel pathway of self-recognition. We are exploring the idea that immune tolerance in mature B cells depends on specific costimulation by self-tissue.
SELECTED PUBLICATIONS
Nemazee, D.A., and K. Bürki. 1989. Clonal deletion of B lymphocytes in a
transgenic mouse bearing anti-MHC class I antibody genes. Nature. 337:562-566.
Nemazee, D.A. and K. Bürki. 1989. Clonal deletion of autoreactive B lymphocytes in bone marrow chimeras. Proc. Natl. Acad. Sci. USA 86, 8039-8043.
Russell, D.M., Dembic, Z., Morahan, G., Miller, JFAP, Bürki, K. and Nemazee, D. (1991) Peripheral deletion of self-reactive B-cells. Nature 354, 308-311.
Tiegs, S.L., Russell, D.M. and Nemazee, D. (1993) Receptor editing in self-reactive bone marrow B-cells. J. Exp. Med. 177, 1009-1020.
Spanopoulou, E., Roman, C.A.J., Corcoran, L., Schissel, M., Silver, D.P., Storb, U., Nemazee, D. , Nussenzweig, M., Shinton, S.A., Hardy, R.R. and Baltimore, D. (1994) Expression of functional immunoglobulin transgenes allows ordered B-cell differentiation to progress in Rag-1 deficient mice. Genes & Devel. 8, 1030-1042.
Nemazee, D. (1995) Antigen receptor "capacity" and the sensitivity of self tolerance. Immunol. Today 17, 25-29.
Rubio, C.F., Kench, J., Russell, D.M., Yawger, R., and Nemazee, D. (1996). Analysis of central B-cell tolerance in autoimmune-prone MRL/lpr mice bearing autoantibody transgenes. J. Immunol. 157, 65-71.
Lang, J.L., Brunmark, A., Jackson, M., Russell, D.M., Yawger, R., and Nemazee, D. (1996). Efficient deletion of immature, but not mature, autoreactive B-cells by ultra-low affinity, membrane-bound self antigens. J. Exp. Med. 184, 1685-1697.
Hertz, M. and Nemazee, D. (1997). BCR ligation induces receptor editing in IgM+D- bone marrow B-cells in vitro. Immunity 6, 429-436.
Melamed, D., Kench, J.A., Rolink, A., and Nemazee, D. (1997). Functional B cell receptor transgene allows IL-7 independent maturation of B cell precursors. J. Immunol. 159, 1233-1239.
Melamed, D. and Nemazee, D. (1997). Self-antigen does not accelerate immature B cell apoptosis, but stimulates receptor editing as a consequence of developemental arrest. Proc. Natl. Acad. Sci. USA 94, 9267-9272.
Lang, J.L., Strasser, A., Korsmeyer, S., Harris, A., and Nemazee, D. (1997). Enforced Bcl-2 expression inhibits antigen-mediated clonal elimination of peripheral B-cells in an antigen dose-dependent manner, and promotes receptor editing in immature B-cells. J. Exp. Med., 186, 1513-1522.
Nemazee, D. (1998). Theoretical limits to massive receptor editing in immature B-cells. Curr. Top. Immunol. Microbiol. 229, 163-171.
Melamed, D., Benschop, R. J., Cambier, J. C., and Nemazee, D. (1998). Developmental regulation of B lymphocyte immune tolerance compartmentalizes clonal selection from receptor selection. Cell 92, 173-182.
Hertz, M., Kouskoff, V., Nakamura, T., and Nemazee, D. (1998). V(D)J recombinase induction in splenic B cells is inhibited by antigen receptor ligation. Nature 394, 292-295.
Kench, J.A., Russell, D. M. and Nemazee, D. (1998). Efficient peripheral clonal elimination of B lymphocytes in MRL/lpr mice bearing autoantibody transgenes. J. Exp. Med., 188, 909-917.
Retter, M.W. and Nemazee, D. (1998). Receptor editing occurs frequently during normal B cell development. J. Exp. Med., 188, 1231-1238.
Kouskoff, V., Kaye, B, Lang, P., Cambier, J., and Nemazee, D. (1998). Partial agonist ligands of the B cell receptor induce differential lymphokine production and partial tyrosine phosphorylation. J. Exp. Med., 188, 1453-1464.
Kouskoff, V., Lacaud, G., Nemazee, D. 2000. T-cell independent rescue of B lymphocytes from peripheral immune tolerance. Science 287, 2501-2503.
Nemazee, D. 2000. Receptor selection in B and T lymphocytes. Annu. Rev. Immunol., 18, 19-51.
Chumley, M.J., Dal Porto, J. M., Kawaguchi, S., Cambier, J.C., Nemazee, D., and Hardy, R.R. 2000. A VH11Vk9 BCR drives generation of CD5+ B cells both in vivo and in vitro. J. Immunol., 164:4586-4593.
Kouskoff, V., Lacaud, G., Retter, M., and Nemazee, D. 2000. B cell receptor expression level determines the fate of developing B lymphocytes: Receptor editing versus selection. Proc. Natl. Acad. Sci. USA, 97: 7435-7439.
Kouskoff, V., Lacaud, G., Nemazee, D. 2000. T-cell independent rescue of B lymphocytes from peripheral immune tolerance. Science 287: 2501-2503.
Melamed, D., Miri, E., Leider, N., Nemazee, D. 2000. Unexpected autoantibody production in membrane Ig-mu-deficient/lpr mice. J Immunol. 165: 4353-4358.
Nemazee, D., Gavin, A. 2003. Do B cells take advantage of "missing self" recognition? Curr. Dir. Autoimmun. 6:245-264.
Gavin, A.L., Ait-Azzouzene, D., Ware, C.F., and Nemazee, D. 2003. delta BAFF, an alternate splice isoform that regulates receptor binding and biopresentation of the B cell survival cytokine, BAFF. J. Biol. Chem. 278:38220-38228.
Quong, M.W., Martensson, A., Langerak, A.W., Rivera, R.R., Nemazee, D. and Murre, C. 2004. Receptor Editing and Marginal Zone B Cell Development are Regulated by the Helix-Loop-Helix Protein, E2A. J.Exp.Med. In press.
Ait-Azzouzene, D., Skog, P., Retter, M., Kouskoff, V., Hertz, M., Lang, J., Kench, J., Chumley, M., Melamed, D., Sudaria, J., Gavin, A., Martensson, A., Verkoczy, L., Duong, B., Vela, J, Nemazee, D. 2004. Tolerance-induced receptor selection: scope, sensitivity, locus specificity, and relationship to lymphocyte-positive selection. Immunol. Rev. 197:219-230.
Gavin, A., Verkoczy, L., Aït-Azzouzene, D., Mårtensson, A., Skog, P., Vela, J., Duong, B. and Nemazee, D. 2004. Peripheral B Lymphocyte Tolerance. Keio J. Med., 53:151-158.
Verkoczy, L.K., Martensson, A.S., Nemazee, D. 2004. The scope of receptor editing and its association with autoimmunity. Curr. Opin. Immunol. 16:808-814.
Gavin, A., Duong, B., Skog, P., Aït-Azzouzene, D., Mårtensson, Greaves, D.R., Scott, M. and Nemazee, D. 2005. ?delta]BAFF, a splice isoform of BAFF, opposes full length BAFF activity in vivo in transgenic mouse models. J. Immunol. 175:319-328.
Ait-Azzouzene, D., Verkoczy, L., Peters, J., Gavin, A., Skog, P., Vela, J.L., and Nemazee, D. 2005. An immunoglobulin C?-reactive single chain antibody fusion protein induces tolerance through receptor editing in a normal polyclonal immune system. J. Exp. Med. 201:817-828.
Collins, C.E., Gavin, A.L., Migone, T.S., Hilbert, D.M., Nemazee, D., Stohl, W. 2005. B lymphocyte stimulator (BLyS) isoforms in systemic lupus erythematosus: disease activity correlates better with blood leukocyte BLyS mRNA levels than with plasma BLyS protein levels. Arthritis Res Ther. 8(1):R6 [Epub ahead of print] .
Verkoczy, L., Ait-Azzouzene, D., Skog, P., Martensson, A., Lang, J., Duong B., and Nemazee, D. 2005. A role for nuclear factor kappa B/rel transcription factors in the regulation of the recombinase activator genes. Immunity 22:519-531.
Ait-Azzouzene, D., Verkoczy, L., Duong, B., Skog, P., Gavin, A., and Nemazee, D. 2006. Split tolerance in peripheral B cell subsets in mice expressing a low level of Ig?-reactive ligand. J. Immunol. 176:939-948.
Ait-Azzouzene, D., Gavin, A., Skog, P., Duong, B., and Nemazee, D. 2006. Effect of cell:cell competition and BAFF expression on peripheral B cell tolerance and B-1 cell survival in transgenic mice expressing a low level of Igkappa-reactive macroself antigen. Eur. J. Immunol. 36:985-996.
Watson LC, Moffatt-Blue CS, McDonald RZ, Kompfner E, Ait-Azzouzene D, Nemazee D, Theofilopoulos AN, Kono DH, Feeney AJ. 2006. Paucity of V-D-D-J Rearrangements and VH Replacement Events in Lupus Prone and Nonautoimmune TdT-/- and TdT+/+ Mice. J Immunol. 15;177(2):1120-8.