Assessment of murine collagen-induced arthritis by longitudinal non-invasive duplexed molecular optical imaging.

OBJECTIVE: In the present study we evaluated the use of four commercially available fluorescent probes to monitor disease activity in murine CIA and its suppression during glucocorticoid therapy. METHODS: Arthritis was induced in male DBA/1 mice by immunization with type II collagen in Complete Freund's Adjuvant, followed by a boost of collagen in PBS. Four fluorescent probes from PerkinElmer in combination [ProSense 750 fluorescent activatable sensor technology (FAST) with Neutrophil Elastase 680 FAST and MMPSense 750 FAST with CatK 680 FAST] were used to monitor disease development from day 5 through to day 40 post-immunization. Fluorescence generated in vivo by the probes was correlated with clinical and histological score and paw measurements. RESULTS: The fluorescence intensity emitted by each probe was shown to correlate with the conventional measurements of disease. The highest degree of correlation was observed with ProSense 750 FAST in combination with Neutrophil Elastase 680 FAST; these probes were then used to successfully assess CIA suppression during dexamethasone treatment. CONCLUSION: We have demonstrated that longitudinal non-invasive duplexed optical fluorescence imaging provides a simple assessment of arthritic disease activity within the joints of mice following the induction of CIA and may represent a powerful tool to monitor the efficacy of drug treatments in preclinical studies.

Tracking lymphocytes in vivo.

The ability to track antigen (Ag)-specific lymphocyte populations in vivo has greatly increased our understanding of the location and functional status of these cells throughout the course of an immune response. Recent technical advances have enhanced researchers' capability to follow migration, activation and cellular interactions of Ag-specific lymphocytes in situ. It is now possible to monitor changes in T cell subsets, co-stimulatory molecules, and chemokine expression within the physiological context of secondary lymphoid organs. Furthermore, the Ag-presenting cell-T cell interaction can be studied,thus dissecting the role and timing of Ag presentation of particular dendritic cell subsets in the initiation of the immune response. The capacity to adoptively transfer small populations of Ag-specific T lymphocytes has also increased our knowledge of the physiologically important role of regulatory T cells in autoimmunity and immunosuppression. New fluorescence imaging techniques such as multicolor video microscopy, laser scanning cytometry, and multiphoton tissue imaging have provided new ways in which researchers can track cellular changes within Ag-specific lymphocytes in vivo. This review summarizes some of the ways in which these techniques have led to discoveries in the role of signaling cascades, cell cycle progression, and apoptosis in maintaining an Ag-specific immune response.