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From the * Department of Microbiology and Immunology, Stanford University Medical Center,
Stanford, California 94305; and Multiple sclerosis is an autoimmune disease thought to be mediated by CD4+ T helper cells
(Th). Experimental autoimmune encephalomyelitis is a rodent model of multiple sclerosis and
has been used extensively to explore a variety of immunotherapies using soluble protein or
peptide antigens. The underlying mechanisms of such therapy have been attributed to induction of T cell anergy, a switch in Th1 to Th2 responses, or peripheral deletion of autoreactive
T cells. In this study, we have developed transgenic mice expressing a T cell receptor (TCR)
specific for the NH2-terminal peptide Ac1-11 of the autoantigen myelin basic protein to explore the mechanism of soluble peptide therapy. T cells from these mice are highly skewed toward the CD4 population and have an abnormal thymic architecture, a phenomenon found in
other TCR transgenic mice that exhibit a highly skewed CD4/CD8 ratio. Soluble Ac1-11 or
the analogues Ac1-11[4A] or Ac1-11[4Y] (which bind to the major histocompatibility complex [MHC] class II molecule I-Au with increasing affinities) given intravenously activates T cells, rendering cells hyperresponsive in vitro for at least two days after injection. Concomitantly,
T cells apoptose in the periphery, the degree of which correlates with the affinity of the peptide for the MHC. In addition, a shift in the T helper phenotype of the surviving T cells occurs
such that the low affinity peptide, Ac1-11, induces primarily a Th1 response, whereas the highest affinity peptide, Ac1-11[4Y], induces primarily a Th2 type response. These data show that
both the nature and the presumed number of the peptide-MHC complexes formed during
specific peptide therapy affect both the degree of peripheral programmed cell death as well as
the outcome of the T helper subset response in vivo, leading to amelioration of disease.
Department of Immunology, Erasmus Universiteit Rotterdam,
Postbus 1738, 3000 DR Rotterdam, The Netherlands
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