Alternative pathways of leucocyte activation that converge to activate type 1 inflammatory genes which, in turn, regulate end stage inflammation in skin and the appearance of the psoriasis phenotype. BRL, Bonzo receptor ligand; DC, dendritic cell; ICAM, intercellular adhesion molecule; ITAC, interferon inducible T cell α chemoattractant; IL, interleukin; IFN, interferon; iNOS, inducible nitric oxide synthase; IP10, interferon inducible protein 10; IRF, interferon regulatory factor; ISF, interferon stimulated factor; LFA-1, leucocyte function associated antigen-1; MCP, monocyte chemoattractant protein; MIG, monokine induced by interferon γ; MIP, macrophage inflammatory protein; MxA, interferon induced cellular resistance mediator protein; NF, nuclear factor; NK, natural killer (cell); PARC, pulmonary and activation regulated chemokine; PNAd, peripheral node addressin; TNF tumour necrosis factor; SLC, secondary lymphoid tissue chemokine; STAT, signal transducer and activator of transcription; VCAM, vascular cell adhesion molecule; VEGF, vascular endothelial growth factor.