CXCL13 and psoriatic arthritis: While some studies concentrate on specific cell subsets, such as the enhanced circulation of memory CD8+ T cells in the skin of patients with psoriatic arthritis (PsA), considered responsible for dysregulating cutaneous immunity and inflammation development [21], or the significance of Tc17 cells (a subset of CD8+ T cells) and CXCL13 (C-X-C Motif Chemokine Ligand 13) in psoriasis [19], few have investigated the coordination of external communication patterns and internal regulatory networks among different cell subsets of psoriasis.