<qa>  What is NF-KB involved in cytokine production?- Patients with previously documented human immunodeficiency virus HIV infection. HIV-positive patients are excluded from the study based on theoretical concerns regarding the effect of PS-341 on certain aspects of immune function. NF-KB is a critical T cell activation protein including through CD40LCD 154 stimulation and also is involved in cytokine production. Because PS 341 effectively blocks NF-KB and therefore could reduce or block the ability of T lymphocytes and other immune cells to fight HIV, PS-341 should not be administered to HIV-positive patients. Additional experiments in animal models are being conducted to better elucidate the effects of PS-341 on HIV. 