While the proportion of CD4+CD25highCD127low regulatory T cells (Treg) was numerically highest in MPE (6.9% in MPE vs. 3.8% in tumor vs. 4.2% in blood), MPE Tregs possessed lower levels of activation markers (CD69, HLA-DR) and co-inhibitory receptor (PD-1, LAG-3, TIM-3) expression (Figure 1C, Figure S5J–M, Figure S7A). Here, CD4 is linked to neoplasm.