BM-APC stimulate helper T cell proliferation. Deer mice were immunized with 20 μg of KLH subcutaneously and 10 days later the lymph nodes, bone marrow and splenocytes were retrieved for expansion of helper T cells and BM-APC. After expansion of these cells in culture, proliferation assays were performed comparing mitomycin-C-treated autologous splenocytes (SC) and BM-APC (BMC) for their capacity to stimulate T cells. In each instance, the BM-APC were more effective at stimulating T cell responses. The data are of two deer mice (DM212 and DM213).