Abstract
BackgroundRapid clonal expansion of T cells occurs in response to antigenic challenges. The kinetics of the T cell response has previously been described using tissue-based studies performed at defined time points. Luciferase bioluminescence has recently been utilized for non-invasive analysis of in vivo biologic processes in real-time.ResultsWe have created a novel transgenic mouse model (T-Lux) using a human CD2 mini-gene to direct luciferase expression specifically to the T cell compartment. T-Lux T cells demonstrated normal homing patterns within the intact mouse and following adoptive transfer. Bioluminescent signal correlated with T cell numbers in the whole body images as well as within specific organ regions of interest. Following transfer into lymphopenic (RAG2-/-) recipients, homeostatic proliferation of T-Lux T cells was visualized using bioluminescent imaging. Real-time bioluminescent analysis of CD4+ T cell antigen-specific responses enabled real-time comparison of the kinetics and magnitude of clonal expansion and contraction in the inductive lymph node and tissue site of antigen injection. T cell expansion was dose-dependent despite the presence of supraphysiologic numbers of OVA-specific OT-II transgenic TCR T-Lux T cells. CD4+ T cells subsequently underwent a rapid (3–4 day) contraction phase in the draining lymph node, with a delayed contraction in the antigen delivery site, with bioluminescent signal diminished below initial levels, representing TCR clonal frequency control.ConclusionThe T-Lux mouse provides a novel, efficient model for tracking in vivo aspects of the CD4+ T cell response to antigen, providing an attractive approach for studies directed at immunotherapy or vaccine design.
Highlights
Rapid clonal expansion of T cells occurs in response to antigenic challenges
We describe the generation of a transgenic mouse (T-Lux) model in which the luciferase gene is expressed by T cells, thereby permitting analysis of T cell population dynamics in living mice in realtime
Red blood cell-depleted peripheral blood was imaged after the addition of luciferin, using the IVIS® imaging system
Summary
Rapid clonal expansion of T cells occurs in response to antigenic challenges. The kinetics of the T cell response has previously been described using tissue-based studies performed at defined time points. BMC Immunology 2009, 10:44 http://www.biomedcentral.com/1471-2172/10/44 through in situ analysis by immunohistologic methods or by isolation and analysis of recovered T cells from disrupted tissues. While each of these approached offers unique advantages (and disadvantages), neither permits "real-time" analysis of T cell dynamics following antigenic exposure and is limited to specific time points and tissues chosen for study. Luciferase proteins produce light in the visible spectrum (approximately 560 nm for firefly luciferase) following interaction with luciferin substrate molecules. This reaction only requires ATP and oxygen and can occur in any actively metabolic cell. Bioluminescence requires relatively short imaging times (seconds to minutes), is easy to use, and the instrumentation is relatively inexpensive [1,2]
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