PRF1 and cancer: As for in vitro settings,activation of CD4+ cells can lead to more pronounced cytotoxiceffects, as these cells are capable of eliminating cancer cells throughthe granzyme perforin pathway.31,66−68 On the other hand, activation of CD4+ T-cells, includingregulatory T-cells (T-regs), in vivo might be associatedwith suppression of immune responses and lower BiTE efficacy.