CD4 and neuroblastoma: It has been suggested that activation state or suppressive functions of the infiltrating T cells greatly depend on the specific microenvironment present in the anatomical site [21]. FOXP3 expression did not correlate to CD4 expression but correlated to PFR1 mRNA levels, further supporting the tenet that FOXP3 mRNA expression in NB tumors was an indicator of effector T-cell activation rather than of immunosuppressive Treg cells [21, 22, 31–33].