To further characterize cytotoxic CD4+ T cells in SFMC, we performed 10X 5 ́single-cell sequencing in combination with TCRαβ sequencing on purified CD4+ T cells from paired SFMC and peripheral blood mononuclear cells (PBMC) from 11 ACPA+ RA patients and 4 ACPA− patients (Fig. 2a and Supplementary Data 1). Here, PRTN3 is linked to rheumatoid arthritis.