It has been established that specific pathogenic infiltrating immune cell subsets, such as IL-1β-positive pro-inflammatory monocytes, autoimmune-associated B cells, and peripheral helper T (Tph) cells sharing similarities with Tfh cells, distinct subsets of CD8+ T cells, as well as mast cells, contribute to the inflammatory pattern of the RA synovial lining/sublining [166,167,168,169,170,171]. Here, CD8A is linked to rheumatoid arthritis.