CD4hiCD8lo DP T cells are the most prominent of the DP cell populations and were found to be significantly more frequent in PBMC from ACPA positive RA patients when compared to healthy controls, SLE patients or ACPA negative RA patients (mean%: RA ACPA+1.93, RA ACPA− 1.07, HD 1.24 and SLE 0.58, figure 1B). Here, PRTN3 is linked to systemic lupus erythematosus.