Trapped in the epineurium: early entry into the endoneurium is restricted to neuritogenic T cells in experimental autoimmune neuritis.

BACKGROUND: Autoimmune polyneuropathies are acquired inflammatory disorders of the peripheral nervous system (PNS) characterized by inflammation, demyelination, and axonal degeneration. Although the pathogenesis has not been fully elucidated, T cells recognizing self-antigens are believed to initiate inflammation in a subgroup of patients. However, the route and time of T cell entry into the PNS have not yet been described in detail. In this study, we analyzed both kinetics as well as localization of retrovirally transfected green fluorescent protein (GFP)-expressing neuritogenic T lymphocytes in experimental autoimmune neuritis (EAN). METHODS: T lymphocytes obtained from rats following EAN induction by immunization with peripheral nerve protein peptide P255-78 were retrovirally engineered to express GFP. Non-specific T cells were negatively selected by in vitro restimulation, whereas GFP-expressing neuritogenic T cells (reactive to P255-78) were adoptively transferred into healthy rats (AT-EAN). Antigen-specific T cell tracking and localization was performed by flow cytometry and immunohistochemistry during the course of disease. RESULTS: After induction of autoimmune neuritis, P2-reactive T cells were detectable in the liver, spleen, lymph nodes, lung, peripheral blood, and the sciatic nerves with distinct kinetics. A significant number of GFP+ T cells appeared early in the lung with a peak at day four. In the peripheral nerves within the first days, GFP-negative T cells rapidly accumulated and exceeded the number of GFP-expressing cells, but did not enter the endoneurium. Very early after adoptive transfer, T cells are found in proximity to peripheral nerves and in the epineurium. However, only GFP-expressing neuritogenic T cells are able to enter the endoneurium from day five after transfer. CONCLUSIONS: Our findings suggest that neuritogenic T cells invade the PNS early in the course of disease. However, neuritogenic T cells cross the blood-nerve barrier with a certain delay without preference to dorsal roots. Further understanding of the pathophysiological role of autoagressive T cells may help to improve therapeutic strategies in immune-mediated neuropathies.

Transplantation of Schwann cells co-cultured with brain-derived neurotrophic factor for the treatment of experimental autoimmune neuritis.

The aim of this study was to investigate the effects of transplantation of Schwann cells (SCs) co-cultured with brain-derived neurotrophic factor (BDNF) for the treatment of experimental autoimmune neuritis (EAN). Primary SCs were co-cultured with various BDNF concentrations, and the optimum concentration was determined by cell proliferation, and NGF and FGF levels. A rat model of EAN was established by immunization with 400µg of P2 peptide dissolved in Freund's complete adjuvant. SCs were labeled with CFSE and injected into the cisterna magna 14days after immunization. We found proliferation of SCs, and NGF and FGF levels were highest at a BDNF concentration of 50ng/mL. Compared with EAN group, SCs+BDNF group showed the lower paralysis scores from day 34 to day 45, and in sciatic nerves showed a significant decrease in inflammatory cell infiltration (involved CD4-, CD8- and CD68-positive cells) at days 25 and 35, an alleviated demyelination at days 35 and 45, and an increase in S-100-positive cells and a decrease in NGF-positive cells at each time point (P<0.05). Compared with the EAN group, the SCs+BDNF group showed, in sciatic nerves, the mRNA level of NGF was significantly decreased but that of S-100 was increased at day 25, the mRNA level of CCL3 was also remarkably reduced at day 35, and the mRNA level of CD11a, CCL3 and NGF was reduced but that of S-100 was elevated at day 45 (P<0.05). There were no differences in results between the SCs group and EAN group. In the end, we draw the conclusions that the exogenous SCs injected through cisterna magna can migrate to the injured peripheral nerves, BDNF promotes the proliferation and secretory function of SCs in vitro, and BDNF-treated SCs in vivo can reduce paralysis, inflammation, and demyelination and improve the self-repair capability of body in EAN.