Kayser O, Masihi KN, Kiderlen AF (2003): Natural products and synthetic compounds as immunomodulators
Expert. Rev. Anti-infect. Ther. 1 (2): 319-335.

Research on immunomodulation by natural products or synthetic derivatives is of key interest for anti-infective therapy for a number of reasons. Many plant remedies well-known in traditional medicine or refined natural products in clinical use exert their anti-infective effects not only (if at all) by directly affecting the pathogen. At least part of their effect is indirect, by stimulating natural and adaptive defense mechanisms of the host. These findings have now given many empirical therapies a rational, scientific basis, and thereby a means for "intelligent" improvement. In discovering the molecular mechanisms by which known remedies exert their effects, chosen elements further down the "chain of command" might be synthesized and applied directly for more rapid and selective cure, omitting unwanted side effects. The direct use of recombinant cytokines, often in combination with antibiotics, is one consequence of this rationale.