PTPN1 and rheumatoid arthritis: PTPN1 (or PTP1B), for example, known to negatively regulate macrophage development and activation through CSF1 signalling32, is upregulated in lympho-myeloid RA patients; similarly, CD28, encoding for the CD80/CD86 receptor and fundamental for T cells/antigen-presenting-cell interaction, is upregulated in lympho-myeloid and the sublining of patients responding to biologic treatments.