DISEASE CHARACTERISTICS: Histologically or cytologically confirmed adenocarcinoma of the prostate with lymphatic, bone, visceral or soft tissue metastases (stage IV) No prostatic transitional cell or small cell carcinoma PSA greater than 4.0 ng/dL Measurable or evaluable disease by PSA OR Bidimensional disease on physical exam or radiologic imaging studies Testosterone less than 50 mg/L if prior hormonal therapy with gonadal ablation (LHRH analogues) or estrogens No previously irradiated or new CNS metastases

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: Karnofsky 70-100% Life expectancy: Greater than 6 months Hematopoietic: WBC at least 3,000/mm3 Absolute lymphocyte count at least 1,000/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9.0 mg/dL Hepatic: Bilirubin less than 2.0 mg/dL No hepatic disease Renal: Creatinine less than 2.5 mg/dL No symptomatic urinary tract infection Cardiovascular: No New York Heart Association class III or IV heart disease Pulmonary: No acute or chronic asthma No chronic obstructive pulmonary disease Other: No history of autoimmune disease (e.g., inflammatory bowel disease, systemic lupus erythematosus, ankylosing spondylitis, scleroderma, or multiple sclerosis) No other concurrent malignancy except nonmelanoma skin cancer or controlled superficial bladder cancer No active acute or chronic infection HIV negative No other medical or psychological condition that would preclude study Adequate peripheral vein access Hepatitis B surface antigen negative Hepatitis C negative

PRIOR CONCURRENT THERAPY: Biologic therapy: At least 6 weeks since prior biologic therapy and recovered No other concurrent immunotherapy Chemotherapy:

At least 6 weeks since prior chemotherapy and recovered No concurrent chemotherapy Endocrine therapy: See Disease Characteristics Greater than 4 weeks since prior flutamide At least 6 weeks since prior bicalutamide Concurrent gonadal androgen suppression with LHRH analogues allowed unless androgen refractory disease At least 6 weeks since prior steroids No concurrent steroids Radiotherapy: See Disease Characteristics At least 6 weeks since prior radiotherapy to the prostate (12 weeks since strontium 89) and recovered No concurrent radiotherapy Surgery: Prior surgical castration allowed Other: No concurrent immunosuppressants (e.g., azathioprine or cyclosporine)