Antibodies against membrane interleukin 1 alpha activate accessory cells to stimulate proliferation of T lymphocytes.

Some monoclonal antibodies (mAbs) against interleukin (IL) 1 alpha 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-1 beta do not activate APC. In the absence of APC, mAbs against IL-1 alpha 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-1 alpha. The observations imply that surface membrane IL-1 alpha can function as a triggering molecule on APC, which could play an important role in the initiation of immune responses by T lymphocytes.