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More MS news articles for April 2003

In vitro evidence that subcutaneous administration of glatiramer acetate induces hyporesponsive T cells in patients with multiple sclerosis

http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=12706402&dopt=Abstract

Clin Immunol 2003 Mar;106(3):163-74
Schmied M, Duda PW, Krieger JI, Trollmo C, Hafler DA.
Laboratory of Molecular Immunology, Center for Neurologic Diseases, Department of Neurology, Brigham and Women's Hospital and Harvard Medical School, 02115, Boston, MA, USA

Glatiramer acetate (GA; Copaxone) is a random sequence polypeptide used in the treatment of relapsing remitting multiple sclerosis (RR MS).

We have recently demonstrated that prior to treatment, GA induces proliferation of resting T cells and is not cross-reactive with myelin antigens.

Daily GA injections induce a significant loss of this GA responsiveness, which is associated with the induction of highly cross-reactive Th2-type T cells potentially capable of suppressing inflammatory responses.

The mechanism of action by which GA induces T cell nonresponsiveness leading to T cell receptor degeneracy in patients with RR MS is unknown.

Here, we examined the effects of daily GA administration on the induction of T cell hyporesponsiveness.

The frequency of GA-reactive T cells in peripheral blood of seven patients with RR MS was measured by limiting dilution analysis prior to and during 6 months of treatment.

In addition, a model in which GA-reactive T cells were stimulated in vitro was developed to better characterize the selection of T cell populations over time.

In vivo treatment with GA induced a decrease in GA-reactive T cell frequencies and hyporesponsiveness of CD4(+) T cell reactivity to GA in vitro that was only partially reversed by the addition of IL-2.

These data suggest that T cell peripheral tolerance to GA was achieved in vivo during treatment.

Thus, our in vitro data suggest that the underlying changes in GA-reactive CD4(+) T cell reactivity could be explained by the induction of T cell anergy and clonal elimination.