Novel Anergy Genes as Markers of Immune Tolerance

Stanford University, Stanford CA

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Abstract

DESCRIPTION (provided by applicant): We intend to use model systems that will allow us to address the hypothesis that peptide tolerance induction, either by the oral or intravenous (IV) route, induces the expression of GRAIL (a recently identified anergy gene) and induces anergy as a form of tolerance. Further, we believe that CD25+ CD4+ T cells may play a role in this form of induced unresponsiveness. Using linear amplification of messenger RNA (mRNA) and subsequent microarray technology, we will examine the genes expressed in CD4+ T cells in these systems in vitro and in vivo. This will be accomplished, in part, by using the adoptive transfer of T cell receptor (TCR) transgenic T cells (with or without co-transfer of CD25+ T cells) into conventional or immuno-deficient mice and analyzing tolerance induction (anergy) imposed by various routes of peptide (normal or altered peptide) administration. The novelty of these proposed studies arises from recent experimental observations in our laboratory. We identified a gene, GRAIL, which functions to block the transcription of interleukin-2 (IL-2) mRNA and whose expression in CD4+ T cells correlates with the phenotype of anergy. As determined by sequence motif searches, this anergy gene encodes a trans-membrane protein whose expression could function to serve as a reliable marker for the allergic (tolerant) state in CD4+ T cells and perhaps in CD8+ T cells and in B cells. We postulate that GRAIL expression will provide a novel and effective screen for the allergic phenotype in mice and in man. The second observation was the elucidation of the role of CD25+CD4+ T suppressor cells. In recent studies, we demonstrated that CD25+CD4+ T cells act as classic suppressor cells when co-cultured with CD25-CD4+ T cells following activation of both sub-populations. The intriguing finding was the up-regulation of GRAIL expression and the blockade of IL-2 message and protein production in the suppressed CD25-cells; anergy in the classic sense. More recent findings have suggested a role for GRAIL expression in peptide-induced tolerance in vivo in mice. Three specific aims are proposed to examine this hypothesis.