Partial purification and identification of an immunosuppressive factor in AIDS sera.

The cause of the profound immunodeficiency state induced by the human immunodeficiency virus (HIV) is not yet fully understood. Although direct cytopathic effects of the virus leading to the loss of CD4+ lymphocytes are believed to play a major role, soluble factors that cause lymphocyte dysfunction have also been identified. Here, we demonstrate that sera of AIDS patients contain a viral component capable of profoundly inhibiting normal T lymphocyte and natural killer cell functions. This factor (M(r) 30,000-50,000) is relatively resistant to proteolytic degradation, heat denaturation, extreme pH, and chemical modifications. It has been determined by Western blotting to share epitopes with the gp41 viral transmembrane component of HIV-1. This immunosuppressive factor has the characteristic property of inhibiting lymphocyte activation in the early stage (within 3 hr) of mitogenic stimulation. Concomitant with the inhibition of lymphocyte activation and interleukin 2 (IL-2) production, transcription of the IL-2 message is also reduced in a time-dependent manner. The unique time dependency of this immunosuppressive factor in lymphocyte activation could serve as a valuable tool to study the early steps of signal transduction in lymphocyte activation beyond membrane interaction.