SAP+ TPH cells constituted 6.3 ± 3.0% of all CD4 T cells in the healthy controls and were expanded to 11.8 ± 6.3% in SLE patients with stable disease (15 patients, p=0.006) and 18.8 ± 8.0% in SLE patients experiencing a flare (15 patients, p<0.0001 compared to healthy controls). Here, SH2D1A is linked to systemic lupus erythematosus.