In vitro induction of specific T cells able to help in the generation of delayed-type hypersensitivity by thymus-dependent and type-II 'thymus-independent' antigens.

An in vitro system is described which supports the primary induction of T cells able to help in the induction of delayed-type hypersensitivity. This system is used to demonstrate that hapten-Ficoll conjugates induce potent hapten-specific T cells with this function. These type-II 'thymus-independent' antigens are thus able to induce specific regulatory T cells. These helper T cells are similar to those induced by classical thymus-dependent antigens in that they are specific for antigen rather than idiotype and act by a linked mechanism.