This invention discloses immunopotentiating agents which stimulate an immune response. These agents are categorized into single agents that act directly, adjuvants added concurrently with the agents, or heteroconjugates. Heteroconjugate agents elicit or enhance a cellular or humoral immune response which may be specific for an 
epitope contained within an 
amino acid sequence. Enhanced hematopoieses by 
bone marrow stem cell recruitment was also a result of administering some of these agents. Examples of immunopotentiating agents include 
monoclonal antibodies and proteins derived from microorganisms (e.g., enterotoxins) which activate T cells. One method of treatment disclosed uses only the immunopotentiating agent to stimulate the 
immune system. Another uses adjuvants in combination with the agent. A third method employs heteroconjugates. Heteroconjugates comprise: (a) an immunopotentiating 
protein which is characterized as having an ability to stimulate T cells; and (b) a second 
protein having an 
amino acid sequence which includes an 
epitope against which a cellular or humoral response is desired. This invention also relates to a method of preparing the heteroconjugate, and to a method of stimulating the 
immune system in vivo in a novel way. One 
route of stimulation is to activate T cells, in some instances, specific subsets of T cells, by administering heteroconjugates containing an immunopotentiating 
protein and a second protein, to mammals. For this method of treatment, the second protein in the heteroconjugate is derived from abnormal or diseased tissue, or from an 
infectious agent; alternatively, the second protein is produced synthetically by 
standard methods of 
molecular biology. Sources of the second protein include tumors, viruses, 
bacteria, fungi, protozoal or metozoal parasites. 
Monoclonal antibodies or T cells prepared from mammals whose immune systems have responded to administration of the heteroconjugate may be produced and administered to induce 
passive immunity. A method of preparing a hybridoma which secretes said 
monoclonal antibodies and use of these 
monoclonal antibodies and T cells, are also disclosed. This invention is also directed to a vaccine comprising the heteroconjugate.