- Determine the toxicity of anti-cytotoxic T-lymphocyte-associated antigen-4 monoclonal antibody in patients with follicular or mantle cell lymphoma, colon cancer, or prostate cancer refractory to vaccine therapy. (part I) (prostate cancer and mantle cell lymphoma closed to accrual as of 3/10/2005; colon cancer closed to accrual as of 9/28/05)