PRF1 and cholestasis: However, although these data suggested that cholestasis and inflammation have induced a switch in immune response toward the CD4+P+ cells, it was also found that higher concentrations of ALT in sera increased the MFI of perforin in CD16+ (r = 0.409; P < .016) and CD56+ cells (r = 0.509; P < .002), suggesting that remaining NK cells, owing to the increased content of P probably obtained a higher cytotoxic activity (Figure 9).