Objective To assess the predictive ability of CD8+ T-cell counts and the expressions of CD28,CD38,HLA-DR on CD8+ T cells in immunocompromised critically ill (ICCI) patients with pulmonary invasive fungal infections (PIFI).Methods The evolution of CD8 + T-lymphocyte subgroups ( CD8+,CD8 + CD28 +,CD8 +CD38 +,CD8 + HLA-DR+ ) were measured in the peripheral blood of 80 ICCI patients with pulmonary infection on day 1 ( D1 ),3 ( D3 ) and 7 ( D7 ) of intensive care unit ( ICU )admission by quantitative flow cytometry. Forty immunocompetent,uninfected critically ill patients were analyzed as control subjects at the time of admission.Immunocompromised risk factors and PIFI was diagnosed according to European Organization for Research and Treatment of Cancer-Mycoses Study Group (EORTC-MSG) 2008 definitions.Results PIFI were diagnosed in 71.3％ of the ICCI patients (57/80)and included 22 molds infections,22 Candida infections and 13 mixed infections.Among the 80 ICCI patients,CD8 +,CD8 + CD28 +,and CD8 + CD38 + T-cell counts were significandy lower ( P ＜ 0.01 ) and CD8 + HLA-DR+ T-cell counts were significantly higher (P ＜0.01 ) than in the control subjects during the monitoring period,while CD8 +,CD8+ CD28 +,and CD8 + CD38 + T cells demonstrated an additional significant decrease in PIFI patients compared with non-PIFI patients ( P ＜ 0.01 ).Receiver operating characteristic (ROC) analysis for discrimination of the 28-day mortality revealed area under the curve(AUC) values of 0.83,0.84 and 0.87 for the CD8+ CD28+ T-cell counts ( D1,D3 and D7,respectively).Cutoff values of D1 ＜64 cells/mm3,D3 ＜75 cells/mm3,and D7 ＜88 cells/mm3 had sensitivities of 0.73(95％ CI:0.61 -0.85),0.74 (95％ CI:0.62-0.85),and 0.71 (95％ CI:0.58-0.84),specificities of 0.90 (95％ CI:0.77 -1.00),0.91(95％ CI:0.78 -1.00),and0.95 (95％ CI:0.85 -1.00),and efficiencies of77.8％,79.5％ and 78.5％ respectively.The time interval between ICU admission and CD8 +CD28+ positive 1.7 days (range:1.0-7.0) was significantly shorter than the time to diagnosis of IFI by radiological 4.1 days ( range:1.0 - 21.0) and microbiological 7.5 days ( range:3.0 - 17.0) criteria ( P ＜0.01 ).Conclusions An extreme distribution of CD8 + T-lymphocyte subgroups in ICCI patients was closely related to PIFI.The measurement of CD8 + CD28+ T-cell counts may be an early predictor of PIFI in ICCI patients.