Functional consequences of noncognate interactions between CD4+ memory T lymphocytes and the endothelium.

The recruitment of Ag-specific T cells to sites of inflammation is a crucial step in immune surveillance. Although the molecular interactions controlling T cell extravasation are relatively well characterized, the effects of these events on T cell function are still poorly understood. Using an in vitro model of transendothelial migration of human CD4(+) memory T cells, we have investigated the molecular and functional changes induced in T cells that come into contact with the endothelium. First, we show that transendothelial migration is precluded by signals that lead to T cell division. In addition, activation of the transcription factor AP-1, without induction of NF-kappaB, is observed in T cells after noncognate interactions with endothelial cells (EC), a pattern of transcriptional regulation different from that observed in dividing T cells. Up-regulation of certain adhesion (CD11a, CD49d), activation (CD69), and costimulatory (CD86) receptors accompany these transcriptional events. Most importantly, recently migrated T cells display a faster rate of migration when reseeded onto an EC monolayer. Finally, T cells become hyperresponsive to antigenic challenge after noncognate interactions with the endothelium. These effects appear not to be due to the selection of preactivated T lymphocytes, because they occur also in clonal T cell populations and appear to be mediated by alpha(L)beta(2) integrin-CD54 interactions. We conclude that CD4(+) memory T cell extravasation is accompanied by phenotypic and functional changes induced by the interactions with the EC, which favor tissue infiltration by T cells and their further activation once they reach the antigenic site.

Zinc-finger protein-targeted gene regulation: genomewide single-gene specificity.

Zinc-finger protein transcription factors (ZFP TFs) can be designed to control the expression of any desired target gene, and thus provide potential therapeutic tools for the study and treatment of disease. Here we report that a ZFP TF can repress target gene expression with single-gene specificity within the human genome. A ZFP TF repressor that binds an 18-bp recognition sequence within the promoter of the endogenous CHK2 gene gives a >10-fold reduction in CHK2 mRNA and protein. This level of repression was sufficient to generate a functional phenotype, as demonstrated by the loss of DNA damage-induced CHK2-dependent p53 phosphorylation. We determined the specificity of repression by using DNA microarrays and found that the ZFP TF repressed a single gene (CHK2) within the monitored genome in two different cell types. These data demonstrate the utility of ZFP TFs as precise tools for target validation, and highlight their potential as clinical therapeutics.