Dynamic Intravital 2-Photon Imaging of Perivascular T Cell – Antigen Presenting Cell Interaction During Induction of Acute Experimental Autoimmune Encephalomyelitis

Lay Summary

Cellular Imaging May Show Immune Interactions During Induction of Animal Model of Multiple Sclerosis

Using cellular imaging, researchers will examine how immune destruction of central nervous system (CNS) cells is initiated in the animal model of autoimmune Multiple Sclerosis (MS).

Immune system functioning is dependent on the spatial and temporal distribution of its individual cells.  The capacity to image individual immune cells within their environment, therefore, may reveal how CNS tissue is attacked by errant immune T cells in the animal model of MS, called “EAE” (experimental autoimmune encephalomyelitis). The investigators developed a method for applying two-photon laser scanning microscopy to directly visualize dynamic immune cell migration and interaction within various tissues in live, anesthetized animals.  Now they will apply this technique to image the interaction between cells of the immune system and the CNS that result in destruction of the myelin sheath that insulates brain cell axons (the communication cables).

They hypothesize that certain immune “antigen presenting cells” (APCs) surrounding blood vessels in the brain may teach immune CD4

⁺ T cells to recognize myelin as foreign, attract these T cells and other immune cells into the brain, and activate them to attack myelin.  The research team will determine what signals are used to selectively attract and retain CD4

⁺ T cells into the brain, how these T cells cross the blood-brain-barrier, and how their destructive activity is sustained.

Significance:  If the research can clarify the cellular and molecular interactions that lead immune cells to destroy myelin in the animal model of autoimmune MS, the findings may lead to new treatments based on methods for interrupting this process.

Abstract

Dynamic Intravital 2-Photon Imaging of Perivascular T Cell - Antigen Presenting Cell Interaction During Induction of Acute Experimental Autoimmune Encephalomyelitis

Timing and sequence of individual cellular recruitment and interactions within tissue microenvironment are critical in shaping the outcome of an immune response toward inflammation versus tolerance. Traditional in vitro and static in vivo approaches to study experimental autoimmune encephalomyelitis (EAE), an animal model of multiple sclerosis (MS), are often inadequate to address the dynamic, migratory, and specific nature of involved immune cells during early induction phase of pathogenic cellular trafficking, recruitment, and infiltration into the CNS milieu. We have previously developed a method of utilizing high-resolution intravital 2-photon laser scanning microscopy (2P-LSM) to visualize immune cell trafficking and dynamic interaction within intact lymph nodes and other peripheral organs of anesthetized experimental mice. This new imaging methodology was instrumental in allowing investigators to uncover the crucial role of in situ tissue architecture and local chemokine gradient in orchestrating proper host immune defenses.

In this proposal we plan to apply this new imaging technique to investigate 1) the potential role of perivascular antigen presenting cells in orchestrating early recruitment of circulating myelin-specific effector CD4⁺ T cells to the CNS of mice with EAE, and 2) the role of local CNS environment in coordinating sequential recruitment and cellular encounters among various immune cell subsets for disease propagation and tissue destruction in EAE.

Success in developing this high-resolution CNS imaging effort, combined with cellular and molecular immunologic approaches, will allow refined understanding in the pathogenesis and establish a platform for in vivo evaluation of future pharmacologic and immunologic therapeutic interventions for MS.