The IL-17 family is composed of six members (i.e., A–F) and is mainly produced not only by Th17 but also by CD8+ T cells, CD4-CD8-γδ T cells, NK cells, innate lymphoid cells (ILC3), mast cells (MCs), and PMNs, yet Th17 are thought to be the main drivers of arthritis (57, 58). Here, IL17A is linked to arthritic joint disease.