CCR7 (EBI1) receptor down-regulation in asthma: differential gene expression in human CD4+ T lymphocytes

Asthma is an inflammatory disorder, and the CD4+ T lymphocyte plays a key role in mediating the inflammatory response. We used a high-density grid, hybridization-based, differential gene expression technology to analyse molecular mechanisms underlying in vivo CD4+ T-cell activation in both steroid-resistant asthma (SRA) and steroid-sensitive asthma (SSA). Hybridization of radioactively-labelled first-strand cDNAs prepared from different biological samples, to identical high-density gridded arrays of PCR amplicons derived from cDNA clone inserts immobilized on nylon membranes, was compared by phosphorimaging. Hybridization data were captured and processed using image analysis software that can identify the location and signal intensity of each hybridized cDNA. This produces a hierarchy of signals of differing intensities between the two grids, representing differential gene expression in the two different RNA samples. CCR7 (EBI1), a lymphocyte-specific G-protein-coupled receptor, was down-regulated in the CD4+ T cells of SRA and SSA non-atopic, compared to non-asthmatic non-atopic individuals. This observation is intriguing given that CCR7 and its ligand EBI1-Ligand Chemokine (ELC), may play a role in the migration and homing of normal lymphocytes. Also, TNFR2 is up-regulated in both SSA non-atopic and SRA atopic as compared to non-asthmatic controls. LAMR1 is down-regulated in CD4+ T cells of SRA compared to non-asthmatic individuals, irrespective of their atopic status. These could be general phenomena resulting from cytokine release.