Search

Experimental autoimmune neuritis (EAN) is a T-cell-mediated autoimmune disease of the peripheral nervous system (PNS) that can be actively induced in Lewis rats by immunization with bovine PNS myelin and Freund's complete adjuvant. EAN is used as an animal model of the Guillain-Barré syndrome (GBS) in humans. To study the potential role of cytokines in EAN, we used in situ hybridization to detect mRNA expression of interleukin 1 beta (IL-1 beta), IL-6, IL-10, IL-12, tumor necrosis factor-alpha (TNF-alpha), TNF-beta, and cytolysin in sciatic nerve sections over the course of EAN. Cells expressing IL-1 beta and IL-6 mRNA appeared early and peaked on Day 7 postimmunization (p.i.), i.e., at onset of clinical signs of EAN, consistent with a role of these cytokine in an early immune response leading to autoaggressive immunity in EAN. TNF-alpha, TNF-beta, and IL-12 mRNA expression was maximally upmodulated on Day 14 p.i., i.e., at height of clinical EAN, favoring a role for these cytokines in disease development. On the contrary, transcription of cytolysin and IL-10 in sciatic nerves reached maxima during clinical improvement of EAN. The data argue for a major proinflammatory role for IL-1 beta, IL-6, TNF-alpha, TNF-beta, and IL-12 and a disease downregulating function for both cytolysin and IL-10 at the target site in EAN. These findings have relevance for future studies on pathogenesis and treatment of GBS in humans.

The present study was undertaken to elucidate the mechanisms responsible for the cytotoxicity of herpes simplex virus (HSV)-specific CD4+ human cytotoxic T lymphocyte (CTL) clones, focusing on perforin and membrane-bound lymphotoxin (LT) (tumor necrosis factor-beta). Two HSV-specific CD4+ CTL clones, which expressed both perforin and membrane-bound LT, exerted HSV-specific cytotoxicity and cytotoxicity against LT-sensitive L929 cells. These CD4+ CTL clones lysed HSV-infected cells directly in an HLA class II-restricted manner and did not exhibit "bystander killing." The culture supernatants of these clones stimulated with HSV antigen showed no cytotoxicity against HSV-infected cells or L929 cells, suggesting that adhesion to target cells is essential to their antigen-specific and antigen-nonspecific cytotoxicities. The cytotoxicities of these clones against HSV-infected autologous cells were inhibited by an anti-CD3 monoclonal antibody but not by an anti-LT antibody. Conversely, their cytotoxicities against L929 cells appeared to be partially inhibited by the anti-LT antibody but not by the anti-CD3 monoclonal antibody. Furthermore, target cell DNA fragmentation induced by these CD4+ CTL clones was apparently observed in L929 cells but only faintly detected in HSV-infected autologous cells. L929 cell DNA fragmentation was also inhibited by adding the anti-LT antibody to CD4+ CTL cultures. These data suggest that some CD4+ CTL possess at least two cytolytic mediators, i.e., perforin and membrane-bound LT simultaneously, and can exert both antigen-specific cytotoxicity via two distinct mechanisms, necrosis and apoptosis.

The ability of various subsets of human mononuclear cells to produce human lymphotoxin (LT) was examined. Peripheral blood mononuclear cells were separated into OKT4+, OKT8+, and Leu-11a+ subpopulations by flow cytometry. Both OKT4+ and OKT8+ cells produced LT upon phytohemagglutinin (PHA) stimulation, but the OKT4+ T cells were the major source of LT. In contrast, Leu-11a+ cells failed to produce LT. The LT production and the proliferative response to PHA, of OKT4+ and OKT8+ cells, were inhibited by prostaglandin E2 and histamine. The LT, derived from PHA-stimulated peripheral blood lymphocytes, was purified by a procedure involving Blue-agarose, Con A-Sepharose chromatography, preparative gradient polyacrylamide gel electrophoresis and preparative sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The LT activity was recovered from SDS gel with major activity peak in the Mr 76,000 region and the minor activity peak in the Mr 24,000 region. The LT derived from 1788 lymphoblastoid cell line also showed heterogeneity on SDS gel. The activity was recovered from two peaks in the region of Mr 70,000 and 20,000.