Suppressor T cells which block the induction of cytotoxic T cells in vivo.

Mice pretreated with cyclophosphamide have an increased ability to produce anti-trinitrophenyl cytotoxic T cells after painting with the contact sensitizing agent picryl chloride. This could be abrogated by injecting normal cells or cells from mice exposed to trinitrophenyl derivatives at the time of painting. If the injection of cells was delayed until 1 day after painting specificity could be demonstrated. Normal cells and cells from mice injected with dinitrobenzene sulphonate were ineffective whereas cells from donors injected with picryl sulphonic acid were inhibitory. Inhibitory cells were also shown in mice painted with picryl chloride, particularly after adult thymectomy. Using this system it was found that cells from picryl chloride but not oxazolone painted mice were inhibitory when injected 1 day after painting the recipients. The suppressor cells from the mice injected with picryl sulphonic acid and from the mice painted with picryl chloride were shown to be cyclophosphamide sensitive T cells and were not affected by adult thymectomy. These properties have helped to classify the suppressor cells induced by trinitrophenyl derivatives.