Front Immunol

OBJECTIVEAutoimmune lymphoproliferative syndrome (ALPS) with FAS mutation (ALPS-FAS) is a nonmalignant, noninfectious, lymphoproliferative disease with autoimmunity. Given the central role of natural regulatory T cells (nTregs) in the control of lymphoproliferation and autoimmunity, we assessed nTreg-suppressive function in 16 patients with ALPS-FAS.RESULTSThe proportion of CD25CD127 Tregs was lower in ALPS-FAS patients than in healthy controls. This subset was correlated with a reduced CD25 expression in CD3CD4 T cells from ALPS patients and thus an abnormally low proportion of CD25FOXP3 Helios T cells. The ALPS patients also displayed a high proportion of naïve Treg (FOXP3CD45RA) and an unusual subpopulation (CD4CD127CD15sCD45RA). Despite this abnormal phenotype, the CD25CD127 Tregs' suppressive function was unaffected. Furthermore, conventional T cells from -mutated patients showed normal levels of sensitivity to Treg suppression.CONCLUSIONAn abnormal Treg phenotype is observed in circulating lymphocytes of ALPS patients. However, these Tregs displayed a normal suppressive function on T effector proliferation . This is suggesting that lymphoproliferation observed in ALPS patients does not result from Tregs functional defect or T effector cells insensitivity to Tregs suppression.KEYWORDSautoimmune lymphoproliferative syndrome-FAS, cell proliferation, human, regulatory T cell, suppression assay