MAP2K1 and Arthritis: After boosting on day 21 with CII emulsified in IFA, DBA1/J mice developed arthritis about seven days later and array analysis of sera collected on day 31 demonstrated autoantibody responses targeting multiple citrullinated epitopes including cfc1, cfc2, cfc3, cfc4, cfc6 and CCP lin 0139-32 (all citrulline-modified peptides derived from filaggrin) (Figure 2c).