Blood to skin recirculation of CD4 memory T cells associates with cutaneous and systemic manifestations of psoriatic disease.

Blood to skin recirculation could play a role in the pathogenesis of psoriasis. To investigate this possibility we dissected the phenotype of circulating T cells in psoriasis patients, calculated the correlation the clinical parameters of the disease and performed a parallel bioinformatics analysis of gene expression data in psoriatic skin. We found that circulating CCR6 CD4 T and T cells significantly correlated with systemic inflammation. Conversely, the percentage of CXCR3 CD4 T cells negatively correlated with the severity of the cutaneous disease. Importantly CLA CD4 T cells expressing CCR6 or CCR4CXCR3 negatively correlated with psoriasis severity suggesting recruitment to the skin compartment. This assumption was reinforced by gene expression data showing marked increase of CCR7 and CLA-encoding gene SELPLG expression in psoriatic skin and strong association of their expression. The data enlightens a role for CD4 T cells trafficking between blood and skin in cutaneous and systemic manifestations of psoriasis.