The present invention relates to an antigenically effective peptide comprising, from the amino to the carboxylic terminal, the amino acid sequence: G P P W W P P I C D P P Q P S K T Q G Q S X1 G Q S X2 G X3 G X4 G X5 G X6 G X7 G K G K S X8 D K Q X9 K P G G P W X10 P E P (SEQ ID No. 1), wherein the amino acids X1-X10 are selected independently from an arginine residue or a citrulline residue and at least one of X1-X10 is a citrulline residue, or a functional fragment thereof and uses thereof.
