Generation and characterization of T-helper cells by primary in vitro sensitization using Langerhans cells.

We have utilized cultured Langerhans cells to activate and expand hapten- and protein-specific T-helper cells from nonsensitized mice. The generation of these lines was strongly dependent on eliminating all autologously reacting cells from the responder T-cell population. Primary in vitro sensitization was not uniquely induced with cultured Langerhans cells as splenic dendritic cells could subserve the same function. Despite its ability to induce strong allogeneic T-cell responses as well as hapten-specific secondary responses, M12c cells, a class II-bearing B-cell lymphoma line, could not activate hapten-specific T-helper cells in vitro. After primary or secondary in vitro stimulation, the T-helper cells which are generated secrete IL-2 and are able to adoptively transfer hapten-specific contact sensitivity, thus stimulating Type-1 T-helper cells. The T-helper cell lines which were generated after repeated cycles of stimulation stimulated type-2 T-helper cells in that they produced IL-4 and depended on this cytokine for autocrine growth. As well, when cultured with syngeneic, hapten-modified, small resting B cells, these T-helper cells caused specific IgE production. Thus, the studies reported herein demonstrate that it is possible to activate and expand T-helper cells with desired specificity from nonsensitized animals in vitro. Previous studies have demonstrated that expansion and adoptive transfer of effector T cells with specificity for tumor-associated antigens may be useful in the control of certain tumors; T-helper cells generated by in vitro sensitization should also be useful in adoptive immunotherapy.