ABSTRACT
Trichosanthin (Tk), a crystal plant protein isolated and purified from root tubes of a Chinese medicinal herb Trichosanthes kiritowii Maxim (Cucurbitaceae), was demonstrated to be capable of inducing immune suppression in man, and the suppression could be eased up by depleting the culture of CD 8~+ cells with monoclonal anti bodies as reported in our previous work (1). This paper desc ribes that the diminition of suppression,or the restoration of low- responsiveness, however, was restricted in certain subjects we studied. For the others, the suppression kept unchanged or even got more vigorous with the same treatment. For this reason, healthy subjects were categoried as CD 8 -mediators (M~+) and non-mediators (M ~- ). In addition, there were some interesting points revealed as follows. 1 ) M~+ and M~- were determined as a phenotipically stable and reproduceable traits; 2) The difference between two categories can only be observed in the MLR- Tk testing system but not in the non-specific PHA- Tk system in which PHA initiated lymphoproliferation was depressed by T K; 3 ) Instead of stimu lator, only responding PBMC in one-way MLC was affectad by depleting CD8 cells, which resulted in the distinguishable phenotypes of M~+ and M~-; 4) The supernatants collected from Tk sensitized. cultured PBMC could show suppressive activity if the cell donors were M~+, but not M~-.