H2BC21 and systemic lupus erythematosus: Histones, which are secreted in NETosis process, are two to three times more acetylated on H2B-K12 and H4-K8, K12, and K16 and methylate on H3-K27 in SLE patients in contrast to healthy individuals, determining the association of the histones acetylation and methylation with apoptosis, NETs, and SLE[73,74].