Compositions that include extracts from sources of immune modulators that include nanofraction immune modulator molecules (i.e., molecules having molecular weights of about 3,000 Da and less) are disclosed. These compositions may also include other immune modulators, such as transfer factor. Administration of compositions with extracts that include nanofraction immune modulator molecules modulates the cell-mediated immunity (e.g., down-regulates undesired T cell activity) of a subject to which such compositions are administered. When administered with transfer factor, the combination of nanofraction immune modulator molecules and transfer factor down-regulates undesired T cell activity while increasing, or up-regulating, T cell activity against pathogens and other undesirable entities, such as cancer cells and other aberrant or mutated cells. Assays and assay techniques for evaluating the immune modulation capabilities of various substances are also disclosed.