CD4 and immune system disorder: Interestingly, we demonstrated here for the first time that typical sepsis-immune dysfunctions such as decreased monocyte HLA-DR expression, decreased circulating CD4+ T-cell count, and increased percentage of regulatory T cells [6] were associated with an increased PD-1 expression on CD4+ lymphocytes (and PD-L1 to a lesser extent) and increased PD-1, PD-L1, and PD-L2 expressions on monocytes.