[Cytotoxic molecules, perforin and serine esterase in cytotoxic T lymphocyte].

Cytotoxic T lymphocyte (CTL) contains two cytotoxic molecules, perforin and serine esterase, in its cytoplasmic granules. These molecules play a key role in CTL-mediated cell lysis, but the precise mechanism has not been fully understood. The author has discovered some of the biochemical characteristics of these cytotoxic molecules. The molecular weight of purified perforin was 66 kd under reducing conditions. Its activity was absolutely dependent on the Ca2+ concentration. The highest activity was seen at 0.2 mM Ca2+ concentration. The Zn2+ ion inhibited the perforin activity in the presence of Ca2+ ion. Heparin increased the pore-forming activity of perforin with highest stimulation at 400 ng/ml. The perforin inhibitor protein, having a molecular weight of 500 kd, was isolated from human serum. This inhibitor suppressed the membrane-binding activity of perforin. The CTL-specific serine esterase detected with the substrate BLT had a molecular weight of 66 kd determined by HPLC gel filtration. The author found that the localization of BLT serine esterase was distinct from that of perforin in CTL. A study into the significance of the difference in the localization of the two molecules is now in progress.