CD4 and Sepsis: Expression levels of PD-1, PD-L1 and PD-L2 on four lymphocyte subsets (CD27 + CD19+ B cells, CD27-CD19+ B cells, CD27 + CD4+ T cells and CD27-CD4+ T cells) were compared between 22 patients with sepsis (including 11 survivors and 11 non-survivors) and 11 healthy controls using flow cytometry.