Transfer factor, also called transport factor, is produced by lymphocytes with a cellular immune function. It transports some antigen-specific cellular immunity of lymphocyte rich cells to unexposed or native some lymphocytes. So it is able to transfer some specific and non-specific cellular functions of the donor to the recipient and amplify the immune response of the recipient. It triggers and regulates the cellular immune function to sensitize some cells that are not exposed to the antigen. It is activated by macrophages, enhancing the ability to recognize, bind, phagocytose and digest antigens by macrophages that are synergistically involved in the immune response. Transfer factor also enhances the production of interleukins, interferons and other human cytokines in the body, adjusts a variety of immune indicators, and acts on several parts of the immune system. It can correct the imbalance of immunity in the body, so that the low or hyper-immune function can be adjusted, so it is also a common drug in dealing with patients with low immunity or immune imbalance.