Jan Gelan

Visualisation of the kinetics of macrophage infiltration during experimental autoimmune encephalomyelitis by magnetic resonance imaging

Macrophages are considered to be the predominant effector cells in multiple sclerosis (MS) and its animal model experimental autoimmune encephalomyelitis (EAE). Ultra small particles of iron oxide (USPIO) can be used to detect macrophage infiltrates in the CNS with magnetic resonance imaging (MRI). Here, we investigated whether the kinetics of lesion formation in EAE can be visualised by altering the time point of USPIO injection and the time interval between particle injection and MRI. When USPIO are systemically injected 24 h before MRI, hypo intense regions are detected in different brain regions depending on the disease stage. These regions correspond to sites of macrophage infiltration. A more complete visualisation of sites of inflammation is accomplished by USPIO injection at disease onset and postponing MRI to top of disease. This study demonstrates that the distribution pattern and amount of inflammatory lesions detected with USPIO, depends on timing of USPIO administration and subsequent MRI. These findings are important for a correct application and interpretation of USPIO dependent contrast imaging of CNS inflammation.

Tracking of myelin-reactive T cells in experimental autoimmune encephalomyelitis (EAE) animals using small particles of iron oxide and MRI

Myelin‐reactive T cells are responsible for initiating the cascade of autoreactive immune responses leading to the development of multiple sclerosis. For better insights into the disease mechanism, it is of major importance to have knowledge on the sites at which these cells are active during disease progression. Herein, we investigated the feasibility of tracking myelin‐reactive T cells, upon labelled with SPIO particles, in the central nervous system (CNS) of experimental autoimmune encephalomyelitis (EAE) animals by MRI. First, we determined the optimal labelling condition leading to a high particle uptake and minimal SPIO–Poly‐l‐lysine (PLL) aggregate formation using Prussian blue staining and inductively coupled plasma spectroscopy measurements. Results from labelling of myelin reactive T cells with low concentrations of SPIO particles (i.e. 25 µg/ml) combined with different concentrations of PLL (0–1.5 µg/ml) showed that increasing amounts of PLL led to augmented levels of free remnant SPIO‐PLL aggregates. In contrast, a low PLL concentration (i.e. 0.5 µg/ml) combined with high concentrations of SPIO (i.e. 400 µg Fe/ml) led to a high labelling efficiency with minimal amounts of aggregates. Second, the labelled myelin‐reactive T cells were transferred to control rats to induce EAE. At the occurrence of hindlimb paralysis, the SPIO labelled myelin‐reactive T cells were detected in the sacral part of the spinal cord and shown to be highly confined to this region. However, upon transfer in already primed rats, T cells were more widely distributed in the CNS and shown present in the spinal cord as well as in the brain. Our study demonstrates the feasibility of tracking SPIO labelled myelin‐reactive T cells in the spinal cord as well as the brain of EAE rats upon systemic administration. Furthermore, we provide data on the optimal labelling conditions for T cells leading to a high particle uptake and minimal aggregate formation. Copyright