CD200 and pulmonary arterial hypertension: Cluster 6 was similar among control and PAH, with some down-regulated genes in cell cycle pathways, but many upregulated genes in processes of angiogenesis, migration, inflammation and cell adhesion (kdr, cxcr4, angiopoietin 2 (angpt2), pgf, platelet derived growth factor subunit B (pdgfb), nid2, jagged canonical notch ligand 2 (jag2), OX-2 membrane glycoprotein (cd200), ccl14).