Faculty active in this area of research are listed below. For a brief description of their research interests, click on their name in the list. Clicking on the name at the beginning of the brief description links to their detailed personal website.
J. Edwin Blalock, PhD The overall objective of our current research is to delineate certain genetic rules that govern the shape and function of proteins and peptides. Specifically, nucleic acids encode amino acid sequences in a binary fashion with regard to hydropathy. We and others have provided compelling evidence that the exact pattern of polar and nonpolar amino acids, rather than the precise identity of particular R groups, is an important driving for protein shape. Structural proof for this idea is being pursued through determination of the 3-dimensional structures of peptides with dissimilar primary amino acid sequences but identical binary codes. These design principles are being used: 1) to make synthetic peptides specifically targeted to act as agonists and antagonists of Ca++ channels involved in human immunodeficiency virus-mediated apoptosis and 2) to make synthetic peptide vaccines as immunotherapeutic agents against autoimmune diseases of the nervous system such as myasthenia gravis (MG) and multiple sclerosis (MS). Additional research areas include: First, together with colleagues at the University of Utrecht, we are evaluating the aforementioned peptide regulators of Ca++ channels for utility in models of asthma. Second, together with Dick Marchase's group, we are elucidating the structure and function of a novel Ca++ influx factor (CIF) which is a key signal for store-operated Ca++ entry. Third, we are studying the role of these CIF-operated channels, as well as their regulation by glucosamine in diabetes.
R. Pat Bucy, MD, PhD Dr. Bucy is interested in the regulation of immune responses by T cells, particularly the forms of regulation that develop in vivo in situations with chronic antigen presence. Conventional experimental systems have used model antigens given in discreet inoculations so that the clearance of antigen is the dominant overall control mechanism. In physiological situations such as solid organ transplantation, chronic viral diseases, and organ specific autoimmune diseases, antigen is usually not cleared, but the immune system develops various control mechanisms that limit immune damage. In addition to his role as the Director of the UAB Medical Scientist Training Program (joint MD/PhD training), Dr. Bucy's lab is engaged in a wide range of projects with a translational focus, that span the gamut of basic mechanistic studies in mice to active design of human clinical trials. Active current projects include use of TCR transgenic mice to study murine heart transplant tolerance, analysis of T cell population dynamics in response to various forms of immunization, studies of viral and cellular dynamics in SHIV infected Rhesus Macaques, and a substantial series of studies focused on therapeutic immunization of HIV infected people and assessment of changes in immune function in these people. In all of these systems, multiple techniques are used including flow cytometry, immunohistochemistry, cell culture techniques, production of novel transgenic mice, real-time RT-PCR,. and in situ hybridization analysis of viral and cellular RNA species.
Peter D. Burrows, PhDDr. Burrow's laboratory is interested in the development and function of B lymphocytes. Immunoglobulin gene rearrangements, as well as a number of poorly understood changes in gene expression, take place as cells progress through this differentiation pathway. We have been using both cellular and molecular approaches to characterize precursors of human B lineage cells and to identify novel genes whose expression is developmentally regulated. Defects in the expression of such genes could lead to immunodeficiency, whereas inappropriate expression might predispose a cell to malignant transformation. His lab has also begun to explore the function of the multifaceted cytokine, transforming growth factor-beta, in regulating B cell development and function and have identified a novel Fc receptor gene that appears to be expressed in the cytoplasm of germinal center B lymphocytes.
David D. Chaplin, MD, PhD Cytokines of the TNF/lymphotoxin (LT) family signal the development of organized lymphoid tissues. Mice deficient in LT-alpha fail to form lymph nodes and Peyer's patches. They also show disturbed spleen white pulp structure, with failure to segregate B cell and T cell zones, and to form primary B cell follicles with clusters of follicular dendritic cells (FDC). TNF also is required for the formation of primary B cell follicles. Infusion of purified LT-expressing B cells restores development of FDC and primary follicle structure. This demonstrates an unexpected role of B cells as organizers of the lymphoid tissue microenvironment in which the B cells themselves ultimately mature. Normal lymphoid architecture is particularly important for the development of mature antibody responses. This manifests itself in failure of antibody affinity maturation in LT-deficient mice, including failure both to form and to express B cell memory responses. Future studies will define additional signals that establish the normal structure of lymphoid tissues and will define the ways this structure supports a properly regulated immune responses, particularly memory B cell responses. Other studies investigate cytokines as regulators of tissue inflammatory responses, particularly allergic inflammation. These studies have shown that in the skin, IL-1 beta is required for recognition that new antigens have penetrated the epidermis. Without IL-1 beta, there is no activation of Langerhans cells (LC), and these LC fail to deliver antigens from the epidermis to draining lymph nodes. These studies have also shown that in the lungs Th2 cell-dependent allergic inflammation is characterized by an influx of both Th1 and Th2 cells. In fact, Th1 and Th2 cells cooperate to elicit the eosinophil-predominant infiltrates that are characteristic of this response. The long-term aim of these studies is to define the signals that initiate recruitment of helper T cells to peripheral tissues and that modulate the character of the inflammatory response. A major signal for this recruitment is locally produced TNF, acting largely through activation of expression of endothelial adhesion proteins that then support Th cell recruitment.
Randall S. Davis, MD Dr. Davis’ laboratory investigates pathways of normal lymphocyte differentiation to determine the mechanisms that contribute to lymphomagenesis, autoimmunity and immunodeficiency. This work largely focuses on an ancient family of Ig-like receptors with tyrosine-based activating or inhibitory signaling potential. A search for possible Fc receptor relatives identified several novel Ig superfamily genes in humans and mice termed Fc receptor-like molecules (FcRL). FcRL family members are preferentially expressed in B lymphocytes and differentially identified in B lineage malignancies. Follow-up studies have identified eight human and seven mouse relatives in total. The recognition of this family has significant implications for understanding connections between innate and adaptive humoral immunity, the regulation and terminal differentiation of B cells into memory and plasma cells, and possibly, the pathogenesis of B cell malignancies and autoimmunity. Their expression patterns, signaling potential, ligands, and translational potential are areas of active investigation.
Louis Justement, PhD Analysis of the Molecular and Functional Role of the Adaptor Protein HSH2. Studies are ongoing to elucidate the functional role that the adaptor protein HSH2 plays in regulating B cell biology. HSH2 is selectively expressed in cells of the B lineage and its expression is up-regulated in response to agonists that promote B cell survival and differentiation, including CD40L, BLyS, LPS and CpG DNA. Studies have demonstrated that HSH2 is able to block BCR-induced apoptosis in the WEHI-231 B cell line, suggesting that this adaptor is expressed as part of a pro-survival program. Future studies will: 1) Identify important regions/motifs of HSH2 that are involved in its pro-survival function; 2) Identify interacting proteins in B lymphocytes and assess their functional importance; and 3) Generate transgenic and conditional knockout mice to examine the importance of HSH2 in regulation of B cell development, activation and differentiation.
Analysis of the Molecular and Functional Role of the Transmembrane Receptor Trem-Like Transcript 2 (TLT2). The genes encoding mouse and human TLT2 were cloned in our laboratory. Subsequent experiments demonstrated that TLT2 is expressed on B cells, neutrophils and macrophages. With respect to the B lineage, TLT2 is expressed early during development, prior to the BCR. Although TLT2 is expressed on all B cells in the periphery, its level is higher on transitional, marginal zone and B-1 B cells when compared to follicular B cells. Expression of TLT2 can be detected on peritoneal macrophages but not on macrophages in other tissues. Finally, TLT2 is expressed on neutrophils and is significantly up-regulated in response to inflammatory stimuli such as LPS. Future studies will: 1) Assess the functional role of TLT2 in immune responses to infectious organisms; 2) Identify the ligand(s) for TLT2 using molecular and biochemical approaches; and 3) Identify interacting signal transduction proteins and associated pathways that mediate TLT2 function in immune cells.
Analysis of Virulence Factors Produced byMycobaterium tuberculosis. Mycobaterium tuberculosis (MTb) is a serious world-wide pathogen that has the ability to survive within host phagocytic cells such as macrophages (MØ). It has been shown that virulent strains of MTb actually secrete a wide range of proteins or virulence factors that presumably alter host cell function. Studies are ongoing to examine the functional role of two secreted virulence factors produced by MTb. The first protein being studied is a protein tyrosine phosphatase called mPtpb, which alters host cell function presumably by dephosphorylating one or more intracellular substrates. Studies will: 1) Identify the mechanism responsible for secretion of mPtpb from MTb; 2) Identify substrates of mPtpb; and 3) Determine the effect that mPtpb has on MØ function. Another protein that is secreted by MTb, called enhanced intracellular survival (Eis) protein, is a putative acetyltransferase. Thus, Eis may regulate transcription in host MØ through its ability to acetylate substrates in the nucleus. Studies will: 1) Determine if Eis is a functional acetyltransferase; 2) Identify substrates in MØ that are acetylated by Eis; and 3) Determine the functional effect that substrate acetylation has on MØ function.
John F. Kearney, PhD The overall research plans of his laboratory are aimed at discovering fundamental cellular and molecular mechanisms involved in the development the development of T and B lymphocytes. The development and establishment of the B cell repertoire is the net result of both genetic and environmental forces. These are dynamic processes beginning with the earliest expression of immunoglobulins in fetal life and continuing throughout life. Immunoglobulin transgenic and knockout mice models are used to define the antigens involved in the selection process, to determine the phenotypes of B cells at different states of differentiation and selection, and to seek out the fetal and adult anatomical sites where positive and negative selection of B cells occurs. The impact of terminal deoxynucleotidyl transferase activity (Tdt) expression on the diversity of immunoglobulin CDR3 regions and the subsequent effects on fetal perinatal and adult B cells, is being addressed by the use of transgenic mice in which N region additions have been introduced during stages of B cell development when such additions are normally absent or minimal. The molecular and cellular differences between B cell subsets are compared in studies on precursor/progeny relationships using newly developed monoclonal antibodies as cellular markers, and the use of a variety of transgenic and knockout mice.
Based on his knowledge of the mechanisms of immune responses in mice he is also involved in understanding the mechanisms of B. anthracis spore-host interactions to facilitate the subsequent design and development of preventive, interventive and diagnostic procedures of the causative organism of Anthrax. He is using mouse models to define protective immune mechanisms against spore entry and to define mechanisms of immunopathology and immune evasion of the ungerminated spores in the host. Mechanisms of spore attachment, routes of spore entry into the body and spore -host interactions within the immune system are being studied. Emphasis is placed on understanding mechanisms of spore entry and immunoregulation in the skin, gastrointestinal tract, respiratory system and also spore passage in the blood. The experiments outlined in this area of research will aid in our understanding of the role that fetal and neonatal B cells play in establishment and maintenance of the normal immune system and will provide insight into their roles in autoimmune diseases, B cell neoplasia, immunodeficiency diseases and the development of more efficient vaccines against anthrax and other disease producing organisms.
Hiromi Kubagawa, MD The main goal of Dr. Kubagawa's research is to define the development and differentiation of lymphoid- and myeloid-lineage cells in the context of exploring the diseases of the immune system. Several cell surface molecules expressed by these cell types are being studied with regard to their structure and function in adaptive and innate immunity. My colleagues and I are currently focusing on two Fc receptor-related molecules: (i) paired immunoglobulin-like receptors, PIR-A (A for activating) and PIR-B (B for braking or inhibitory), and (ii) the Fc receptor for IgA and IgM (Fcalpha/muR).
Previous findings in Dr. Kubagawa's lab and others' led to the hypothesis that PIR-A and PIR-B play specific regulatory roles in host defense, including inflammatory, coagulative, antigen-presenting, allergic and humoral immune responses. This hypothesis is currently being tested in the following aims: (i) to identify the PIR ligands and (ii) to determine the functional consequences of PIR-B deficiency in a gene-targeted mouse model.
After the serendipitous discovery of a murine cDNA that encodes a protein able to bind the Fc portion of both IgA and IgM, designated as Fcalpha/muR, Dr. Kubagawa's lab has sought to characterize the tissue distribution, structure and function of this receptor. Preliminary findings using receptor specific mAb and RT-PCR analysis indicate an interesting cellular distribution of the human Fcalpha/muR: germinal centers with the appearance of follicular dendritic cells (FDC) in tonsils, proximal tubular epithelial cells in kidneys and Paneth cells in small intestinal crypts. Another remarkable finding is that human Fcalpa/muR is expressed by a small subpopulation of B cells that reside in tonsils, but not in the circulation; hence the expression pattern differs from that of mouse Fcalpha/muR, which is expressed by both circulating and resident B cell populations. A novel splice variant that may encode a soluble form of Fcalpa/muR has been identified in the kidney. These findings led to the hypothesis that Fcalpha/muR plays multiple functional roles depending upon the cell types expressing it. Fcalpha/muR on FDC may trap IgM or IgA immune complexes and present the intact antigens to B cells in germinal centers. Fcalpha/muR expression by B cells may be closely linked with cellular activation. Fcalpha/muR in renal tubular epithelial cells and intestinal Paneth cells on the other hand may play a protective role at portals of entry for antigens and microorganisms. This hypothesis is currently tested by the following aims: (i) to determine the function of the membrane-bound Fcalpha/muR, (ii) to define the newly identified Fcalpha/muR splice variant as a soluble form of the receptor, and (iii) to employ an Fcalpha/muR-deficient mouse model to explore the in vivo function of the Fcalpha/muR.
Dennis F. Kucik, MD White blood cell adhesion to blood vessel walls constitutes an essential early step in the defense against infection, without which an immune response cannot develop. On the other hand, too much adhesion can lead to atherosclerosis and other major health problems. Using a flow-cell system that mimics conditions in the blood vessel, dynamic adhesion is analyzed by high-time-resolution digital imaging and computer analysis. Cultured endothelium and leukocytes from knockout mice enable us to define the functions of specific adhesion molecules. We also use time-lapse imaging of migrating cells to understand endothelial wound healing, and a laser-tweezers-based system to measure adhesion molecule rearrangement on living cells. This work is also important to understand how cancer cells metastasize to distant sites via the bloodstream.
John D. Mountz, MD, PhD A hallmark of autoimmune disease is the development of autoantibodies that can cause disease. My laboratory has identified that the second recombinant inbred strain of B6 x DBA/2 (BXD2) spontaneously produces very high levels of pathogenic autoantibodies. Single antibodies produced by hybridomas from spleens of these mice transfer arthritis or glomerulonephritis in normal mice. By 3 months of age, the spleens of BXD2 mice are greatly enlarged and are packed with numerous large, spontaneous germinal centers (GCs). This GC development is promoted by high levels of Th17 and IL-17 in these mice. IL-17 signals through the IL-17a receptor in B cells resulting in increased classical NF-κB pathway activation. This activates several genes, including regulators of G-protein signaling (RGS) 13 and 16. Upregulation of RGS genes impairs signaling through CXCR4/CXCL12 and CXCR5/CXCL13 to arrest migration and movement of T cells and B cells. This enables prolonged and stable interaction of B cells and CD4 T cells. Key ongoing questions in my laboratory include what is the mechanism for increased Th17 development. IL-6 is highly produced by B cells, macrophages and plasmacytoid dendritic cells (PDCs). TGF-β, however, is not greatly increased. What are the factors, in combination with IL-6, that promote high Th17 development in BXD2 mice? How does Th17 signal through B cells? Our recent evidence indicates that IL-17 signaling requires both TRAF6 and ACT1, which has been identified in IL-17 signaling pathways. Current ongoing work is to determine the mechanism of increased NF-κB signaling in response to IL-17 in B cells. Also using RGS13 KO and RGS16 KO mice, we wish to determine which of these RGS proteins is highly essential for development of spontaneous autoreactive GCs. We also wish to identify the most promising points for interruption of IL-17 signaling that upregulates RGS expression in B cells. Other studies include detailed analysis of the effect of IL-17 on B cell chemotaxis in response to CXCL12 and CXCL13. These include in vitro chemotactic chamber analysis, and live imaging analysis using confocal microscopy.
A second area of interest is the role of DR5 apoptosis in arthritis and autoimmune Disease. TRAIL-DR5 apoptosis signaling is very similar to FAS apoptosis signaling involving mitochondrial amplification loop and Bcl-2 family members, as well as direct induction of apoptosis through caspase activation resulting in terminal caspases 3, 5, and 7 activation. The TRAIL-DR5 apoptosis signaling pathway, like Fas, is inhibited by FLIP-L and XIAP (inhibitors of apoptosis proteins). DR5 is upregulated on synovial fibroblasts of patients with rheumatoid arthritis and in Collagen-II mouse model of arthritis. To determine mechanisms of DR5 apoptosis in vivo, we have produced a human-mouse (hu/mo) chimeric DR5 transgenic mouse. This mouse transgene is driven by the 3 kB mouse DR5 promoter and is regulated by a Floxed-STOP between the promoter and the hu/mo chimeric DR5 transgene. Thus, expression of hu/mo DR5 chimeric transgene can be targeted to synovial fibroblasts, B cells, T cells, or macrophages. In collaboration with Dr. Tong Zhou, we are analyzing the ability of a novel anti-human DR5 antibody (TRA8) to regulate arthritis and immune responses in these chimeric DR5 transgenic mice.
My laboratory has longstanding interest in age-related immune senescence. We were one of the first investigators to propose that T cell senescence is due to decreased, rather than increased, apoptosis. This was directly demonstrated using a CD2-Fas Tg mouse that resulted in increased expression of Fas throughout the lifespan of the mouse. This resulted in decreased T cell senescence. Our recent interest in T cell senescence is being carried out in a study of nonagenarians in collaboration with Dr. Michal Jazwinski (Tulane University) and Dr. Donald Scott (University of Pittsburgh). Nonagenarians are protected from immune senescence by several factors including increased levels of certain hormones, such as leptin and Insulin like growth factor binding protein 3 (IGFBP3). Our ongoing studies are further characterizing methods to prevent immunosenescence with aging. This is relevant to preservation of immune responses tat may help prevent development of cancer, and provide adequate protection against viruses.
Harry W. Schroeder, Jr., MD, PhD Ultimately, it is the identity and specificity of the lymphocyte antigen receptor that determines the nature of the immune response to antigen. The mechanisms that underlie the diversification of the B- and T-cell antigen receptor repertoires appear to generate receptor diversity at random. However, repeated examples of near to absolute identity of receptor sequences between individuals suggest the existence of genetically programmed constraints that may be designed to bias the immune system to produce preferred, and perhaps optimal, repertoires. The implication is that violation of these programs could lead to immune dysfunction, and thus to disease. To test this hypothesis, we are developing mouse models wherein we force expression of altered, polyclonal repertoires that violate normal constraints on antigen receptor sequence or structure. In the first of these mice, where we have forced expression of arginine, histidine and asparagine in the HCDR3 interval of immunoglobulin H chains, we observed somatic selection against antigen binding sites that contained an excess number of these charged amino acids, yet the system ultimately failed to recapture the tyrosine and glycine residues normally encoded by wild-type germline sequence. B-cell development was impeded, immunity to influenza virus was impaired, and expression of IgG anti-DNA antibodies was enhanced. These results support the view that optimal distinction between self and non-self is a product of evolutionary selection.
Trygve O. Tollefsbol, PhD Telomerase, a ribonucleoprotein that maintains the ends of chromosomes, has been the subject of intense investigation due to its potential role in aging and neoplastic transformation. Human chromosomes contain telomeric 5'-TTAGGG-3' repeats for up to 15 kilobases which help preserve chromosomal integrity by preventing rearrangements, degradation and end-to-end fusions. Telomerase synthesizes telomeres and is of great interest because the absence of this enzyme, due to its down-regulation in early embryonic cellular differentiation, appears to contribute to cellular senescence. In normal somatic cells, each cell division is associated with the loss of 30-150 bps of telomeric DNA. This attrition continues with cellular proliferation until a critical minimum length associated with growth arrest and cellular senescence occurs. Strong support for a central role for telomerase in aging has come from studies in which differentiated cells transfected with vectors expressing the human telomerase catalytic subunit, hTERT, have been immortalized. These findings point to hTERT expression as the rate-limiting factor in telomerase activity and bring the study of hTERT gene expression to the forefront of telomerase and aging research. Moreover, cancer increases markedly during the aging process and telomerase is up-regulated in up to 95% of cancer cells which show no net loss of average telomere. Telomerase activity can be detected in the early stages of most common cancers; high levels of telomerase correlate with a poor prognosis for several types of cancers; and ablation of telomerase expression leads to telomeric attrition and growth inhibition of cultured neoplastic cells. It is clear that telomerase is linked to aging and cancer but the mechanisms controlling telomerase in these processes are unknown and constitute the focus of our work.
1) Regulation of the telomerase gene in aging cells. Telomerase is down-regulated during embryonic differentiation and reactivated in most cancer and immortalized cells indicating that this enzyme is reversibly controlled. In all examined cases, hTERT mRNA expression parallels telomerase activity, strongly implicating transcriptional mechanisms of telomerase regulation. Our studies are focusing on the mechanisms of telomerase gene control in aging cells. We have found that the hTERT gene is down-regulated in differentiating human teratocarcinoma cells through mechanisms such as histone deacetylation and DNA methylation. The promoter region of hTERT is currently being analyzed to elucidate the causes for its down-regulation during early embryonic differentiation.
2) Control of telomerase in neoplastic transformation. Although telomerase is active in most cancer cells and appears to be involved in the genesis of neoplastic transformation, the mechanisms of telomerase reactivation in cancer cells are unknown. Our studies are focusing on the role of c-Myc/Mad1 in control of hTERT gene regulation in cancer cells and the role of chromatin alterations and DNA methylation in modulating this process.
3) Cell Senescence Culture Facility. Our laboratory directs a Cell Senescence Culture Facility that provides various types of aging cells to investigators nationwide. This facility is only one of a few in the United States and is designed to not only facilitate studies of aging, but to also participate in new investigations in the mechanisms of cellular aging and age-related diseases such as cancer.
Mark R. Walter, PhD The Walter lab is interested in protein-protein interactions and structural biology of macromolecular complexes required to elicit effective host immune responses against pathogens. Studies have focused on the IL-10 family (IL-10, IFN-γ, IL-20, IL-22, IL-24, IL-26, IL-28, and IL-29) of cytokine receptor complexes that play essential roles in the development and control of the adaptive immune response. The inter-cellular communication provided by these molecules is controlled by a dazzling array of protein-protein interactions that our lab is unraveling. We also study the structure and function of virally encoded proteins produced by herpesviruses and poxviruses that target the IL-10 family and allow the viruses to escape elimination by the immune system. Understanding the competing molecular strategies used by the host and virus to activate or deactivate the immune system may to lead novel ways of controlling chronic inflammation and/or improving the detection and elimination of persistent viral infections. The lab performs the techniques required to answer mechanistic questions about molecular recognition, viral immune evasion, and cell signaling including protein biochemistry, X-ray crystallography, Surface Plasmon Resonance, computational and bioinformatic approaches, and structure-based functional assays in cells.
Casey Weaver, MD The research in my laboratory concerns the mechanisms by which CD4 T cells control adaptive immunity. Major current projects are: the generation and characterization of transgenic and knock-in mouse models for tracking T cell fate during CD4 effector and memory T cell development (Saparov et al., Immunity 11:271, 1999; Hurez et al., J. Exp. Med., 198:123, 2003); studies defining mechanisms that induce development of the Th17 effector lineage (Harrington et al., Nature Immunology 6:1123, 2005); characterization of mechanisms by which dysregulation of CD4 T cells leads to inflammatory bowel disease (Iqbal et al., J. Exp. Med., 195:71, 2002; Elson et al., Curr. Opinion in Gastroenterology 20:360, 2004); delineation of the adhesion pathways that control effector T cell trafficking (Mangan et al., Amer. J. Pathology, in press); and, characterization of the genetic elements that regulate cytokine gene expression in Th1 and Th17 cells (Dzialo-Hatton et al., J. Immunol. 166:4534, 2001).