The laboratory of Garnett Kelsoe studies the molecular- and population genetics of B lymphocytes during their development from hematopoietic precursors and following their activation by antigen. Dr. Kelsoe is a member of the Duke Autoimmunity Center of Excellence, the Collaboration for AIDS Vaccine Discovery, and is a member of the CHAVI-ID Scientific Leadership Group. In addition, the laboratory is closely allied with Duke’s Center for the Study of Aging and Human Development, the Comprehensive Cancer Center, and the Center for AIDS Research. The laboratory staff, Dongmei Liao, Xiaoe Liang, Wenli Zhang, Xiaoyan Nie, Hanqin Peng, and Margaret Barker, provide outstanding research capacity and administrative expertise.
Kelsoe and his collaborators have long been interested in the development, differentiation, and antigen-receptor repertoire of B lymphocytes and have made significant observations on V(D)J recombination, development of the primary antibody repertoire, immune regulation by antigen-receptor interaction, germinal centers as sites of somatic evolution, the origins of autoimmunity, and mechanisms of central B-cell tolerance. The Kelsoe laboratory first has demonstrated the origins and dynamics of germinal center B- and T-cell populations, the germinal center as the primary site for B-cell hypermutation and affinity-driven selection, the migration of antigen-specific CD4 T cells between germinal centers, the relationship between memory B cells and long-lived plasmacytes, and patterns of AID expression during B-cell development and differentiation. The recent discovery that “dark antigen” drives proliferation, survival, and selection of germinal center B cells that have no detectable affinity for the immunogen indicates that our models to explain affinity maturation are significantly incomplete.
Heavy Chain Receptor editing unbound ( Garnett H. Kelsoe D. Sc.)
With all of the certainty of death and taxes, questions regarding the mechanisms of immunological tolerance remain fixtures across the landscape of immunology. From Paul Ehlirch’s “horror autotoxicus” (reviewed in ref. 1) to the current synthesis of tolerance by apoptosis, anergy, and receptor editing (2), the mechanisms of immunological tolerance remain, despite substantial research effort, enigmatic.
In PNAS, Kumar et al. (3) and Sun et al. (4) refine our understanding of receptor editing, a principle component of immune tolerance, by demonstrating that at least one form of this tolerance pathway is not driven by reaction with self-antigens.
B lymphocytes respond to specific antigen ligands, via antigen receptors [B-cell receptors (BCR)] that are assembled by variable (V), diversity (D), and joining (J) [V(D)J] recombination, a process of directed genomic rearrangements that fuses V, D, and J gene segments into functional immunoglobulin genes (5, 6). The combinatorial and junctional diversity created by V(D)J rearrangement is thought to be capable of generating approximately 1014 distinct BCRs that are first expressed on the surface of immature B cells. This extraordinary potential for diversity has costs: V(D)J recombination often generates self-reactive BCRs that may instigate autoimmune disease (7, 8).http://dx.doi.org/10.1073%2Fpnas.1501480112
Generation of high-affinity and class-switched antibody requires the germinal center (GC) reaction after infection or immunization. Within the B-cell follicles of secondary lymphoid organs, the GC represents a sophisticated collaboration between antigen-specific B cells, follicular dendritic cells, T follicular helper (TFH) cells and T follicular regulatory (TFR) cells. Despite intensive interest in the development and effector function of TFH and TFREG cells, little is known regarding the selection of T-cell receptor (TCR) repertoire during polyclonal GC reactions. In order to evaluate native, polyclonal TCR responses elicited by a complex antigen, we developed a sorting strategy to isolate TFH/TFREG cell populations that were activated and expanded after immunization. Analysis of the antigen-specific TCR repertoire of TFH/TFREG cells provides important insights into the factors influencing T-cell recruitment and clonal expansion following infection or vaccination, especially when linked to contemporary analysis of the GC B-cell repertoire. These findings may inform rational and selective control strategy of the GC reaction. Vaccine development can accordingly focus on modulating TFH/TFREG responses to facilitate optimal adaptive immune responses.
Modeling affinity maturation (Masayuki Kuraoka, Ph.D., Akiko Watanabe, Ph.D.)
This work is carried out in collaboration with other members of the DHVI (Thomas B. Kepler, Stephen C. Harrison) and Harvard Medical School (Frederick W. Alt). Clonal competition and affinity maturation of B cells take place in GCs and these biological processes are essential to generate high affinity antibodies that can provide protection from infectious agents, such as influenza and HIV-1. Through cycles of experiments, modeling, and validation, this study seeks to develop a mathematical model for somatic hypermutation, clonal selection and affinity maturation in the germinal centers (GCs). Experimental data obtained through the use of 1) wildtype mice as well as mice engineered to express restricted B-cell antigen receptors, 2) high-throughput single B-cell cloning, and 3) structural information for selected clonally related antibodies would be used to develop a model and validate the model developed. This laboratory characterize B-cell repertoire in GCs and memory compartment isolated from human and mouse vaccine studies through a novel high-throughput B-cell culture system that allows the isolation of heavy and light chain pairs from individual B cells as well as measurement of the avidity of the antibody encoded by these genes.