Tajie H. Harris


  • BS, Bemidji State University
  • PhD, University of Wisconsin-Madison
  • Postdoc, University of Pennsylvania

Primary Appointment

  • Assistant Professor, Neuroscience


Research Interest(s)

Immune response to infectious disease in the CNS

Research Description

Toxoplasma gondii is an intracellular, protozoan parasite that infects approximately one-third of the world population. The parasite can be acquired congenitally or in adults, through the ingestion of contaminated food or water. Acute infection with T. gondii leads to systemic disease that is largely controlled by the cytokine, IFN-g. Despite this, the parasite persists in several tissues, including the brain and retina, where an ongoing T cell-mediated immune response is necessary to limit parasite replication. The vast majority of infections are asymptomatic, but suppression of T cell function can lead to severe toxoplasmic encephalitis and/or retinochoroiditis. While the importance of T cells in controlling T. gondii in the brain and eye has been demonstrated, research in the Harris laboratory aims to identify factors within immune-privileged tissues that influence local resistance to T. gondii.

Recently, Dr. Harris examined the CD8+ T cell response in the brain during chronic T. gondii infection using multi-photon (MP) microscopy and mathematical modeling. Statistical analysis revealed that T cell migration is described by a generalized Lečvy walk (GLW), which is characterized by alternating runs and pauses. The GLW is similar to foraging strategies utilized by a variety of species from microzooplankton to monkeys. Subsequent mathematical modeling predicted that the chemokine, CXCL10, contributes to the immune response by decreasing the amount of time required for CD8+ T cells to reach infected target cells. These studies also raised several questions: Is the GLW behavior unique to CD8+ T cells? What additional chemokines affect T cell migration? How do CNS resident cells influence T cell migration? To address these questions, the Harris laboratory will use MP microscopy and other cutting-edge techniques to provide insight into the orchestration of local immune responses in the brain and retina.

Selected Publications

  • Banigan E, Harris T, Christian D, Hunter C, Liu A. Heterogeneous CD8+ T cell migration in the lymph node in the absence of inflammation revealed by quantitative migration analysis. PLoS computational biology. 2015;11(2): e1004058. PMID: 25692801 | PMCID: PMC4334969
  • Louveau A, Smirnov I, Keyes T, Eccles J, Rouhani S, Peske J, Derecki N, Castle D, Mandell J, Lee K, Harris T, Kipnis J. Structural and functional features of central nervous system lymphatic vessels. Nature. 2015. PMID: 26030524 | PMCID: PMC4506234
  • Harris T, Banigan E, Christian D, Konradt C, Tait Wojno E, Norose K, Wilson E, John B, Weninger W, Luster A, Liu A, Hunter C. Generalized Lévy walks and the role of chemokines in migration of effector CD8+ T cells. Nature. 2012;486(7404): 545-8. PMID: 22722867 | PMCID: PMC3387349
  • John B, Ricart B, Tait Wojno E, Harris T, Randall L, Christian D, Gregg B, De Almeida D, Weninger W, Hammer D, Hunter C. Analysis of behavior and trafficking of dendritic cells within the brain during toxoplasmic encephalitis. PLoS pathogens. 2011;7(9): e1002246. PMID: 21949652 | PMCID: PMC3174247
  • Sansing L, Harris T, Welsh F, Kasner S, Hunter C, Kariko K. Toll-like receptor 4 contributes to poor outcome after intracerebral hemorrhage. Annals of neurology. 2011;70(4): 646-56. PMID: 22028224 | PMCID: NIHMS469371
  • Harris T, Wilson E, Tait E, Buckley M, Shapira S, Caamano J, Artis D, Hunter C. NF-kappaB1 contributes to T cell-mediated control of Toxoplasma gondii in the CNS. Journal of neuroimmunology. 2010;222(1): 19-28. PMID: 20156658 | PMCID: PMC2860689
  • Norose K, Kikumura A, Luster A, Hunter C, Harris T. CXCL10 is required to maintain T-cell populations and to control parasite replication during chronic ocular toxoplasmosis. Investigative ophthalmology & visual science. 2010;52(1): 389-98. PMID: 20811054 | PMCID: PMC3053287
  • John B, Harris T, Tait E, Wilson E, Gregg B, Ng L, Mrass P, Roos D, Dzierszinski F, Weninger W, Hunter C. Dynamic Imaging of CD8(+) T cells and dendritic cells during infection with Toxoplasma gondii. PLoS pathogens. 2009;5(7): e1000505. PMID: 19578440 | PMCID: PMC2700268
  • Wilson E, Harris T, Mrass P, John B, Tait E, Wu G, Pepper M, Wherry E, Dzierzinski F, Roos D, Haydon P, Laufer T, Weninger W, Hunter C. Behavior of parasite-specific effector CD8+ T cells in the brain and visualization of a kinesis-associated system of reticular fibers. Immunity. 2009;30(2): 300-11. PMID: 19167248 | PMCID: PMC2696229