Abstract: Provided are an agent for inhibition of cancer development, an agent for improvement of antibody productivity, and an agent for treatment of hepatitis. The agents have been completed by finding that cancer development is inhibited in a healthy subject by administering NK cells, and antibody productivity is improved by administering NK cells and a vaccine to a patient.

Abstract: Provided are an agent for inhibition of cancer development, an agent for improvement of antibody productivity, and an agent for treatment of hepatitis. The agents have been completed by finding that cancer development is inhibited in a healthy subject by administering NK cells, and antibody productivity is improved by administering NK cells and a vaccine to a patient.

Abstract: The present invention provides an immunotherapeutic agent and immunotherapy allowing the extension of the survival time of patients with pancreatic cancer. The immunotherapy of the present invention is characterized by comprising the steps of culturing peripheral blood lymphocytes of a patient with pancreatic cancer by stimulating the lymphocytes with an anti-CD3 antibody and an anti-CD52 antibody, thereby to obtain an immunotherapeutic agent, and administering at least four infusions of the resultant immunotherapeutic agent to the same patient, wherein each of the infusions of the immunotherapeutic agent comprises at least 15×109 cells of activated lymphocytes, the percentage of CD3? CD56+ NK cells in the activated lymphocytes is at least 30%, and the administration of the immunotherapeutic agent is begun for the patient who is in at least one state of two or more particular immunocompromised states.