HDAC9 and rheumatoid arthritis: Hence, these hyperacetylatedhistones cannot stop the activation of proinflammatory genes, ultimatelypromoting inflammation in RA patients.173 There are different types of HDAC: class I includes HDAC-1, 2, 3,and 8, and class II includes HDAC-4, 5, 6, 7, 9, and 10.