To confirm T cell co-stimulation through SLAMF6 and SLAMF3 in SLE, we stimulated PBMCs isolated from SLE patients with anti-CD3 antibodies alone or in the presence of activating anti-SLAMF6 or anti-SLAMF3 antibodies (immobilized stimulation, Figure 1C). Here, LY9 is linked to systemic lupus erythematosus.