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Abstract:
Redirection of body defenses and immunity through manipulation of the immune response is the basis of immunology. Use of vaccines and similar products to stimulate immunity is an implementation of this concept. Attempts to induce immunity against intracellular bacteria, most metazoal parasites, and various tumors have not been highly successful, chiefly because of the difficulty in identifying and isolating the immunogen responsible for inducing protection. Whereas most viruses have only 4 or 5 antigens, bacteria have many more and metazoal parasites may possess hundreds. For this reason, immunologists are investigating alternate methods for inducing immunity or increased resistance. Use of transfer factor (TF) and nonspecific stimulators, such as Bacillus Calmette-Guerin ((BCG) vaccine, are examples.