CTLA4 and neoplasm: The results showed that the abundance of immunosuppressive cells in tumour immunity, such as CD11b+LOX− neutrophils, CD14+HLA-DR− M-MDSCs, CD11b+CD33+CD14−HLA-DR− e-MDSCs and CD14+HLA-DR+ monocytes, was significantly higher in the group with low levels of apoE; also, the abundance of CD3+CD4+PD-1+ T lymphocytes was significantly higher in the abnormal level apoE patient groups than in the normal level apoE group, while the abundance of CD3+CD8+CTLA-4+ T lymphocytes was significantly higher in the low level apoE group than in the normal level apoE group.