Immunological response to mistletoe (Viscum album L.) in cancer patients: a four-case series.

European mistletoe (Viscum album) has been used in complementary cancer treatment, but little is known concerning its effects on immunological parameters, although there is evidence that Viscum may stimulate the immune system. In this study, a trial was conducted with cancer patients to determine whether Viscum album extracts could improve the results of immune tests. These were: white blood cell count (leukocytes, neutrophils, lymphocytes), CD4+ and CD8+ T-lymphocytes, intradermal tests of delayed hypersensitivity (candidin, trichophytin, purified protein derivative-PPD), complement C3 and C4, and immunoglobulin A, G and M. Four patients received seven doses of subcutaneous Viscum album 20 mg, twice weekly. Immunological tests were carried out before and after treatment, and an increase in several parameters of humoral and cellular immunity were shown. Apart from reactions around the injection sites, treatment was well tolerated and all patients benefited from it. These results suggest that Viscum album can enhance humoral and cellular immune responses in cancer patients, but further studies attesting to the possible clinical impact of these immunological effects are necessary.