An anti-inflammatory polypeptide comprising an amino acid sequence of an IL-37 polypeptide, wherein the polypeptide has at least 75% sequence identity to the amino acid sequence of SEQ ID NO: 1 over the full length of the polypeptide; wherein the anti-inflammatory polypeptide comprises a mutation or modification that reduces the capacity of the anti-inflammatory polypeptide to form a dimer compared to a polypeptide comprising the sequence of SEQ ID NO: 1, wherein the mutation or modification is at any one or more residues, or residues equivalent to, 71 to 74, 78, 80, 83 to 88 and 184 in SEQ ID NO: 1, wherein the amino acid residue at, or equivalent to: position 71 in SEQ ID NO: 1 is not a Val; position 72 in SEQ ID NO: 1 is not an Leu; position 73 in SEQ ID NO: 1 is not a Asp; position 74 in SEQ ID NO: 1 is not a Ser; position 78 in SEQ ID NO: 1 is not an Ile; position 80 in SEQ ID NO: 1 is not a Val; position 83 in SEQ ID NO: 1 is not a Lys; position 84 in SEQ ID NO: 1 is not an Asn; position 85 in SEQ ID NO: 1 is not a Tyr; position 86 in SEQ ID NO: 1 is not an Ile; position 87 in SEQ ID NO: 1 is not an Arg; position 88 in SEQ ID NO: 1 is not a Pro; and/or position 184 in SEQ ID NO: 1 is not an Asn preferably wherein the mutation is a replacement with a non-conservative amino acid, or wherein the mutation is replacement with alanine or an amino acid with an opposite charge. wherein the polypeptide has at least 75% sequence identity to the amino acid sequence of SEQ ID NO: 1 over the full length of the polypeptide; wherein the anti-inflammatory polypeptide comprises a mutation or modification that reduces the capacity of the anti-inflammatory polypeptide to form a dimer compared to a polypeptide comprising the sequence of SEQ ID NO: 1, wherein the mutation or modification is at any one or more residues, or residues equivalent to, 71 to 74, 78, 80, 83 to 88 and 184 in SEQ ID NO: 1, wherein the amino acid residue at, or equivalent to: position 71 in SEQ ID NO: 1 is not a Val; position 72 in SEQ ID NO: 1 is not an Leu; position 73 in SEQ ID NO: 1 is not a Asp; position 74 in SEQ ID NO: 1 is not a Ser; position 78 in SEQ ID NO: 1 is not an Ile; position 80 in SEQ ID NO: 1 is not a Val; position 83 in SEQ ID NO: 1 is not a Lys; position 84 in SEQ ID NO: 1 is not an Asn; position 85 in SEQ ID NO: 1 is not a Tyr; position 86 in SEQ ID NO: 1 is not an Ile; position 87 in SEQ ID NO: 1 is not an Arg; position 88 in SEQ ID NO: 1 is not a Pro; and/or position 184 in SEQ ID NO: 1 is not an Asn position 71 in SEQ ID NO: 1 is not a Val; position 72 in SEQ ID NO: 1 is not an Leu; position 73 in SEQ ID NO: 1 is not a Asp; position 74 in SEQ ID NO: 1 is not a Ser; position 78 in SEQ ID NO: 1 is not an Ile; position 80 in SEQ ID NO: 1 is not a Val; position 83 in SEQ ID NO: 1 is not a Lys; position 84 in SEQ ID NO: 1 is not an Asn; position 85 in SEQ ID NO: 1 is not a Tyr; position 86 in SEQ ID NO: 1 is not an Ile; position 87 in SEQ ID NO: 1 is not an Arg; position 88 in SEQ ID NO: 1 is not a Pro; and/or position 184 in SEQ ID NO: 1 is not an Asn preferably wherein the mutation is a replacement with a non-conservative amino acid, or wherein the mutation is replacement with alanine or an amino acid with an opposite charge.