Antibodies Against Membrane Interleukin 1α Activate Accessory Cells to Stimulate Proliferation of T Lymphocytes

Some monoclonal antibodies (mAbs) against interleukin (IL) 1α have been found to activate antigen-presenting cells (APC, human peripheral blood monocytes and B lymphocytes), so that unstimulated T lymphocytes cultured with them are induced to proliferate and secrete IL-2. Control mAbs of the same isotypes and mAbs against IL-11β do not activate APC. In the absence of APC, mAbs against IL-1α do not induce proliferation of T lymphocytes. Mitomycin C-treated activated APC still induce T-cell proliferation. Proliferation of T lymphocytes cannot be induced by culture supernatants and requires contact with APC activated by mAbs against IL-1α. The observations imply that surface membrane IL-1α can function as a triggering molecule on APC, which could play an important role in the initiation of immune responses by T lymphocytes.