Modulation of effector cell functions in experimental autoimmune encephalomyelitis by leflunomide--mechanisms independent of pyrimidine depletion

J Leukoc Biol. 2004 Nov;76(5):950-60. doi: 10.1189/jlb.0504308. Epub 2004 Aug 24.


Leflunomide inhibits de novo pyrimidine synthesis and is a novel, immunosuppressive agent that has been successfully used to treat rheumatoid arthritis. Here, we investigated the efficacy of leflunomide and its mode of action in experimental autoimmune encephalomyelitis (EAE), which is a T helper cell type 1 cell-borne disease model to simulate inflammatory aspects of multiple sclerosis and was induced in Lewis rats by adoptive transfer of myelin basic protein (MBP)-specific T line cells. Given in vivo for 7 days after cell transfer, leflunomide suppressed clinical signs of disease even in uridine-substituted animals. MBP-specific T line cells that had been antigen-activated in vitro in the presence of A77 1726 (active metabolite of leflunomide) produced less interferon-gamma, whereas interleukin (IL)-10 secretion had a tendency to be increased without changes in signal transducer and activator of transcription 6 trafficking. Furthermore, these T cells exhibited reduced chemotaxis and induced a significantly mitigated disease course upon transfer into naive rats. The effects of leflunomide on MBP-specific memory type T line cells in vitro may not be mediated by pyrimidine depletion, as they were not reversible by exogenous uridine. Moreover, A77 1726 led to increased expression of CD86 (B7-2) and secretion of IL-10 in cultured microglial cells in vitro, strengthening their down-modulatory impact on activated, autoantigen-specific T cells. In conclusion, our observations underline that the immunomodulatory potential of leflunomide in effector cells of EAE is clinically relevant and is not exclusively dependent on the depletion of cellular pyrimidine pools.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adoptive Transfer
  • Animals
  • Animals, Newborn
  • Antigens, CD / metabolism
  • B7-2 Antigen
  • Cells, Cultured
  • Chemotaxis, Leukocyte / genetics
  • Chemotaxis, Leukocyte / immunology
  • Disease Models, Animal
  • Encephalomyelitis, Autoimmune, Experimental / drug therapy*
  • Encephalomyelitis, Autoimmune, Experimental / immunology*
  • Encephalomyelitis, Autoimmune, Experimental / metabolism
  • Guinea Pigs
  • Immunosuppressive Agents / pharmacology
  • Interferon-gamma / metabolism
  • Interleukin-10 / metabolism
  • Interleukin-2 / immunology
  • Interleukin-2 / pharmacology
  • Isoxazoles / pharmacology*
  • Leflunomide
  • Membrane Glycoproteins / metabolism
  • Microglia / drug effects
  • Microglia / immunology
  • Microglia / metabolism
  • Multiple Sclerosis / drug therapy
  • Multiple Sclerosis / immunology
  • Multiple Sclerosis / metabolism
  • Myelin Basic Protein / genetics
  • Myelin Basic Protein / immunology
  • Pyrimidines / metabolism*
  • Rats
  • Rats, Inbred Lew
  • STAT6 Transcription Factor
  • T-Lymphocytes, Helper-Inducer / drug effects*
  • T-Lymphocytes, Helper-Inducer / immunology*
  • Trans-Activators / metabolism
  • Uridine / metabolism
  • Uridine / pharmacology


  • Antigens, CD
  • B7-2 Antigen
  • Cd86 protein, rat
  • Immunosuppressive Agents
  • Interleukin-2
  • Isoxazoles
  • Membrane Glycoproteins
  • Myelin Basic Protein
  • Pyrimidines
  • STAT6 Transcription Factor
  • Trans-Activators
  • Interleukin-10
  • Interferon-gamma
  • Leflunomide
  • Uridine