Immunomodulatory Effects of Single-Component and Complex Homeopathic Preparations: A Review of Two Decades of Experimental Research

Background: Highly diluted homeopathic preparations have been investigated as biological response modifiers. This narrative review integrates findings from two decades of experimental research conducted at the Federal University of Parana on single-component homeopathic preparations and the M1, M2, and M8 complexes, emphasizing macrophage function, reactive oxygen and nitrogen species, cytokine production, lymph nodes and hematopoietic-cell phenotypes, and experimental models of melanoma and leishmaniasis. The seven single-component preparations evaluated-Aconitum napellus, Arsenicum album, Atropa belladonna, Bryonia alba, Lachesis muta, Mercurius solubilis, and Thuja occidentalis-produced preparation- and potency-dependent changes in macrophage morphology, nitric oxide, superoxide, hydrogen peroxide, cytokines, and bone-marrow and lymph-node cell markers. The M1, M2, and M8 complexes also displayed distinct profiles. M1 and M8 modulated reactive species and cytokines, while M1 additionally reduced nuclear factor kappa B activation and was associated with antitumor and antileishmanial effects in preclinical models. M8 reduced experimental melanoma lung nodules and perlecan expression. M2 produced a distinct hematopoietic profile.