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

- Increased circulating CCR6+ CD4+ TEM/TEFF cells associated with systemic inflammation in psoriasis patients.
- CXCR3+ CD4+ TEM cells negatively correlated with cutaneous psoriasis.
- Skin-tropic CLA+ CD4+ TCM cells inversely correlated with psoriasis severity suggesting recruitment to the psoriatic skin.
- Marked increase of CCR7 and CLA-encoding gene expression in psoriatic skin and association with the expression of CD4.
- Role for CD4+ T cells trafficking between blood and skin in cutaneous and systemic manifestations of psoriasis.

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+ TEM and TEFF cells significantly correlated with systemic inflammation. Conversely, the percentage of CXCR3+ CD4+ TEM cells negatively correlated with the severity of the cutaneous disease.Importantly CLA+ CD4+ TCM cells expressing CCR6+ or CCR4+ CXCR3+ 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.