However, the level of CD4+CD25+CTLA-4+ cells were remarkably higher in SCLC than that in control, (7.09±5.09)% vs (1.91±1.27)%, P < 0.001 and CD8+PD-1+ cells were less in SCLC than that in control, (11.47±5.85)% vs (22.56±4.21)%, P < 0.001, both of which were not associated with age, sex, smoke or disease stage. Here, CTLA4 is linked to small cell lung carcinoma.