Supplementary Material for: TCRαβ⁺CD4⁻CD8⁻ (double-negative) T cells may predict pathological kidney findings in patients with suspected lupus nephritis

Introduction
T-cell receptor (TCR) αβ⁺CD4⁻CD8⁻ (double-negative) T cells (DNT) exist as a small population of lymphocytes in the peripheral blood of healthy individuals, but have been reported to be increased in autoimmune lymphoproliferative syndrome (ALPS) and other collagen diseases, such as systemic lupus erythematosus (SLE), and to be involved in disease activity. However, there are no reports on their relationship with histological classification of lupus nephritis, influencing the management of SLE.
Methods
The study included 15 patients with SLE who underwent kidney biopsy for suspected lupus nephritis at Toranomon Hospital from June 2014 to March 2019 and also had their peripheral DNT cell levels measured. We defined high DNT as more than 1.5% DNT among peripheral blood lymphocytes, in accordance with the ALPS diagnostic criteria, and divided patients into a High and Low DNT group.
Results
In the 15 cases analyzed, mild glomerular lesions tended to be more common in patients in the high DNT group than those in the low group (60% vs 10%, respectively; p = 0.077, Fisher's exact test), as did moderate to severe leukocytic inflammation in the interstitium (100% vs 20%, respectively; p = 0.004, Fisher's exact test).
Conclusions
Elevated peripheral DNT cell levels may be associated with mild glomerular lesions but moderate to severe interstitial inflammation in SLE patients. A prospective clinical study with a larger patient cohort is warranted to validate this possibility and investigate its potential causality.