Thymus derived inhibitor of lymphocyte proliferation : III—Partial purification and characteristic biological activity

A crude factor isolated from bovine thymus was partially purified using ion exchange chromatography. The resulting fraction was tested for inhibitory properties towards the proliferation of various human and murine lymphoid cells in culture. It was found that this partially purified thymic factor (TF) strongly inhibited the proliferation of lymphocytes induced by mitogen, antigen or allogeneic stimuli with minimal effects on spontaneous proliferation. The inhibition was partially reversible and at the level of the lymphocyte rather than through mediation by non-lymphoid cells. Data obtained in kinetic studies suggest that TF interferes with an early event in the stimulation process, resulting in delayed lymphocyte proliferation