Search

In studying autoimmune diseases of the human peripheral nervous system (PNS), in vitro studies involving the use of cultured rat Schwann cells, neurons, and disease-inducing immune system cells have provided basic information about disease pathogenesis. For example, T-cells that induce experimental allergic neuritis have been shown in vitro to damage Schwann cells, the target cell in these diseases. However, before making contact with Schwann cells, these T-cells must first pass through the blood-nerve barrier. Despite the importance of this interaction, no studies employing PNS endothelial cells in coculture with dorsal root ganglia cells to mimic the environment of the blood-nerve barrier have been reported. This paper describes a simple method for the isolation and culture of peripheral nerve vascular endothelial cells from adult rats that should facilitate in vitro studies of the blood-nerve barrier. Endothelial cells were identified by their expression of an endothelial cell marker, Factor VIII/von Willebrand factor. Their identity was further confirmed by their inability to express Thy 1.1, a fibroblast marker, and their in vitro morphology. Purity of endothelial cell cultures was ensured by a regular program of Thy 1.1 complement depletion of fibroblasts.

P2 protein is found in Schwann cells of the peripheral nervous system (PNS) in vivo and is a component of the myelin sheath. In previous studies by the authors, there have been indications that in vitro, Schwann cells can process and present endogenous P2 peptides to P2-specific T-cells capable of effecting experimental allergic neuritis (EAN) in the Lewis strain of rat. EAN is an animal model of Guillain-Barré syndrome, a human autoimmune disease of the PNS. However, previous studies have shown no evidence of expression of P2 protein by Schwann cells. Therefore, the aim of this study was to determine whether P2 is present in freshly dissociated Lewis rat Schwann cells and thus an endogenous source of peptides. In contrast to previous studies, we found P2 to be present in detectable levels within the cytoplasm of most Schwann cells up to 1 week in vitro, with the level of expression varying from cell to cell.

Interactions between CD4+ P2-specific T-cell lines and Schwann cells were examined in vitro by scanning electron microscopy (SEM) and T-cell proliferation studies. CD4+ T-cell lines clustered around and attached to Schwann cells which expressed Major histocompatibility complex (MHC) class II molecules. Only those P2-specific T-cell lines capable of inducing experimental allergic neuritis (EAN) when injected into adult Lewis rats clustered around the Schwann cells. T-cell lines responsive to P2 but not able to induce EAN did not cluster around Schwann cells. The addition of exogenous P2 protein inhibited in a dose-dependent way clustering and proliferation of the P2-specific T-cell lines. Cytoplasmic P2 was detected in Schwann cells by immunofluorescent labelling and the results of proliferation assays in this study suggest that endogenous P2 protein was processed by the Schwann cells and presented to T-cell lines in association with MHC class II molecules. The clustering and proliferation of class II-restricted CD4+ P2-specific T-cell lines in the presence of Schwann cells provides evidence for a role for Schwann cells as facultative antigen presenting cells, processing and presenting 'self' endogenous antigen to CD4+ T-cell lines capable of inducing EAN.

The cytotoxic effects of CD4+ P2-specific T-cell lines on Schwann cells were examined in vitro with 51Cr-release cytotoxicity assays. Only those P2-specific T-cell lines capable of inducing EAN when injected back into adult Lewis rats were cytotoxic to the Schwann cells. The addition of exogenous P2 protein was not necessary for the cytotoxic effect. The monoclonal antibody (mAb) OX6 directed against Major histocompatibility complex (MHC) class II molecules blocked cytotoxicity, indicating an essential role for MHC class II molecules in this interaction between CD4+ T-cell lines and Schwann cells.

The expression of major histocompatibility complex (MHC) class I and II molecules by Lewis rat Schwann cells after infection with West Nile virus (WNV) in vitro was examined by fluorescence microscopy and flow cytometry. WNV enhanced the expression of MHC class I molecules and induced the expression of MHC class II molecules by Schwann cells. Irradiated medium from WNV-infected Schwann cell cultures upregulated class I molecule expression on dissociated Schwann cell cultures but did not induce the expression of class II molecules. This finding has implications for virally triggered autoimmune diseases of nervous tissue.