IL17A and psoriatic arthritis: IL-17 (primarily IL-17A) is produced by Th17, CD8+ T, and group 3 ILC (ILC3) and participates in many pro-inflammatory processes and autoimmune diseases.193–195 Targeting IL-17 is now regarded as a common strategy to reduce the burden of several autoimmune diseases such as psoriasis and psoriatic arthritis.