MAPK9 and rheumatoid arthritis: Phosphorylation of these two MAPK members, ERK and JNK/SAPK, together with the finding that 14-3-3η is present in the serum of 60% to 82% of early RA patients [8], is consistent with the observations reported by de Launay et al.: that ERK and JNK, but not p38MAPK, are preferentially phosphorylated in early RA [19].