CTLA4 and autoimmune lymphoproliferative syndrome: These include the expansion of TCRαβ CD4−CD8− (double-negative) T cells in autoimmune lymphoproliferative syndrome (ALPS), CD19hi21lo B cells in CVID with autoimmunity, an abnormal count of Treg in Tregopathies, Th17 cells in STAT1 GOF patients, and expanding follicular helper T cells (Tfh) in CTLA4 and LRBA deficiency.