Julie Ledford
Assistant Professor, BIO5 Institute
Assistant Professor, Clinical Translational Sciences
Assistant Professor, Immunobiology
Associate Professor, Cellular and Molecular Medicine
Primary Department
Department Affiliations
(520) 626-0276
Work Summary
Julie Ledford's research focuses on respiratory disease, and genetic and molecular mechanisms of allergic airway diseases in children.
Research Interest
Dr. Ledford’s current work in the area of pulmonary surfactant immunobiology combines her knowledge of mouse genetics, pulmonary disease models and immune function regulation and focuses on understanding the role of Surfactant Protein-A (SP-A) and how it regulates signaling pathways within various immune cell populations. Specifically, she is interested in how SP-A regulates degranulation, either directly or indirectly, of two important cell types in asthma: mast cells and eosinophils. More recently, Dr. Ledford’s research has focused on understanding how genetic variation within human SP-A2 alters functionality of the protein in relation to eosinophil activities and how this translates to characteristics observed in human asthma.

Publications

Ledford, J. G., Voelker, D. R., Addison, K. J., Wang, Y., Nikam, V. S., Degan, S., Kandasamy, P., Tanyaratsrisakul, S., Fischer, B. M., Kraft, M., & Hollingsworth, J. W. (2015). Genetic variation in SP-A2 leads to differential binding to Mycoplasma pneumoniae membranes and regulation of host responses. Journal of immunology (Baltimore, Md. : 1950), 194(12), 6123-32.
BIO5 Collaborators
Monica Kraft, Julie Ledford

Mycoplasma pneumoniae is an extracellular pathogen that colonizes mucosal surfaces of the respiratory tract and is associated with asthma exacerbations. Previous reports demonstrate that surfactant protein-A (SP-A) binds live M. pneumoniae and mycoplasma membrane fractions (MMF) with high affinity. Humans express a repertoire of single-amino acid genetic variants of SP-A that may be associated with lung disease, and our findings demonstrate that allelic differences in SP-A2 (Gln223Lys) affect the binding to MMF. We show that SP-A(-/-) mice are more susceptible to MMF exposure and have significant increases in mucin production and neutrophil recruitment. Novel humanized SP-A2-transgenic mice harboring the hSP-A2 223K allele exhibit reduced neutrophil influx and mucin production in the lungs when challenged with MMF compared with SP-A(-/-) mice. Conversely, mice expressing hSP-A2 223Q have increased neutrophil influx and mucin production that are similar to SP-A(-/-) mice. Using tracheal epithelial cell cultures, we show that enhanced mucin production to MMF occurs in the absence of SP-A and is not dependent upon neutrophil recruitment. Increased phosphorylation of the epidermal growth factor receptor (EGFR) was evident in the lungs of MMF-challenged mice when SP-A was absent. Pharmacologic inhibition of EGFR prior to MMF challenge dramatically reduced mucin production in SP-A(-/-) mice. These findings suggest a protective role for SP-A in limiting MMF-stimulated mucin production that occurs through interference with EGFR-mediated signaling. SP-A interaction with the EGFR signaling pathway appears to occur in an allele-specific manner that may have important implications for SP-A polymorphisms in human diseases.

Huang, C., Jiang, D., Francisco, D., Berman, R., Wu, Q., Ledford, J. G., Moore, C. M., Ito, Y., Stevenson, C., Munson, D., Li, L., Kraft, M., & Chu, H. W. (2016). Tollip SNP rs5743899 modulates human airway epithelial responses to rhinovirus infection. Clinical and experimental allergy : journal of the British Society for Allergy and Clinical Immunology, 46(12), 1549-1563.
BIO5 Collaborators
Monica Kraft, Julie Ledford

Rhinovirus (RV) infection in asthma induces varying degrees of airway inflammation (e.g. neutrophils), but the underlying mechanisms remain unclear.

Hsia, B. J., Ledford, J. G., Potts-Kant, E. N., Nikam, V. S., Lugogo, N. L., Foster, W. M., Kraft, M., Abraham, S. N., & Wright, J. R. (2015). Correction notice for TNF-R on mast cells regulate airway responses to Mycoplasma pneumoniae. The Journal of allergy and clinical immunology.
BIO5 Collaborators
Monica Kraft, Julie Ledford
Foster, M. W., Thompson, J. W., Ledford, J. G., Dubois, L. G., Hollingsworth, J. W., Francisco, D., Tanyaratsrisakul, S., Voelker, D. R., Kraft, M., Moseley, M. A., & Foster, W. M. (2014). Identification and Quantitation of Coding Variants and Isoforms of Pulmonary Surfactant Protein A. Journal of proteome research, 13(8), 3722-32.
BIO5 Collaborators
Monica Kraft, Julie Ledford

Pulmonary surfactant protein A (SP-A), a heterooligomer of SP-A1 and SP-A2, is an important regulator of innate immunity of the lung. Nonsynonymous single nucleotide variants of SP-A have been linked to respiratory diseases, but the expressed repertoire of SP-A protein in human airway has not been investigated. Here, we used parallel trypsin and Glu-C digestion, followed by LC-MS/MS, to obtain sequence coverage of common SP-A variants and isoform-determining peptides. We further developed a SDS-PAGE-based, multiple reaction monitoring (GeLC-MRM) assay for enrichment and targeted quantitation of total SP-A, the SP-A2 isoform, and the Gln223 and Lys223 variants of SP-A, from as little as one milliliter of bronchoalveolar lavage fluid. This assay identified individuals with the three genotypes at the 223 position of SP-A2: homozygous major (Gln223/Gln223), homozygous minor (Lys223/Lys223), or heterozygous (Gln223/Lys223). More generally, our studies demonstrate the challenges inherent in distinguishing highly homologous, copurifying protein isoforms by MS and show the applicability of MRM mass spectrometry for identification and quantitation of nonsynonymous single nucleotide variants and other proteoforms in airway lining fluid.

Ledford, J. G., Lo, B., Kislan, M. M., Thomas, J. M., Evans, K., Cain, D. W., Kraft, M., Williams, K. L., & Wright, J. R. (2010). Surfactant protein-A inhibits mycoplasma-induced dendritic cell maturation through regulation of HMGB-1 cytokine activity. Journal of immunology (Baltimore, Md. : 1950), 185(7), 3884-94.
BIO5 Collaborators
Monica Kraft, Julie Ledford

During pulmonary infections, a careful balance between activation of protective host defense mechanisms and potentially injurious inflammatory processes must be maintained. Surfactant protein A (SP-A) is an immune modulator that increases pathogen uptake and clearance by phagocytes while minimizing lung inflammation by limiting dendritic cell (DC) and T cell activation. Recent publications have shown that SP-A binds to and is bacteriostatic for Mycoplasma pneumoniae in vitro. In vivo, SP-A aids in maintenance of airway homeostasis during M. pneumoniae pulmonary infection by preventing an overzealous proinflammatory response mediated by TNF-α. Although SP-A was shown to inhibit maturation of DCs in vitro, the consequence of DC/SP-A interactions in vivo has not been elucidated. In this article, we show that the absence of SP-A during M. pneumoniae infection leads to increased numbers of mature DCs in the lung and draining lymph nodes during the acute phase of infection and, consequently, increased numbers of activated T and B cells during the course of infection. The findings that glycyrrhizin, a specific inhibitor of extracellular high-mobility group box-1 (HMGB-1) abrogated this effect and that SP-A inhibits HMGB-1 release from immune cells suggest that SP-A inhibits M. pneumoniae-induced DC maturation by regulating HMGB-1 cytokine activity.