BACKGROUND: Chemokines represent a superfamily of immune-modulatory small protein molecules that regulate leukocyte migration to inflammatory sites through their chemoattractant and cell signaling properties. This review focuses on the immunological functions of the CCR6 chemokine receptor and is chemokine ligand, CCL20, that contribute to it role in inflammation in human psoriasis. METHODS: Peer-reviewed relevant articles are searched and selected from 2000 to 2022 using the search engines including PubMed and Google Scholar. RESULTS: After selectively reviewing and evaluating over seventy articles, a comprehensive overview on the immunology of CCL20-CCR6 axis in psoriasis and psoriatic arthritis, the X-ray crystal structures of CCL20 monomers, and the potential of developing clinical therapies targeting this axis is summarized. CONCLUSIONS: Over the past decade, preclinical studies carried out in animal models of psoriasis involving agents targeting CCL20-CCR6 axis have yielded promising results. Other studies that this axis may play a role in a number of other autoimmune diseases, including rheumatoid arthritis, suggesting a rationale for further investigation into this key signaling/migratory pathway.

Although psoriasis and psoriatic arthritis (PsA) have been classically considered to be diseases of the skin and joints, respectively, emerging evidence suggests that a combination of innate and environmental factors creates widespread immune dysfunction, affecting multiple organ systems. A greater understanding of the pathogenesis of psoriasis and the systemic effects of psoriatic inflammation has allowed for the development of new, more effective treatments. The second portion of this two-part review series examines the comorbidities associated with psoriasis and PsA as well as the most recent advances in targeted systemic therapies for these conditions.