CTLA4 and Immunodeficiency: Costimulatory proteins Cd274 (PD-L1), Ctla4 and Cd86 linked to the immune deficiencies observed in sepsis6,19 were upregulated across tissues (12/13 tissues for Cd274, 6/13 tissues for Cd86 and 3/13 tissues for Ctla4; Fig. 1b,c).