Demonstration of specifically sensitized lymphocytes in patients treated with an aqueous mistletoe extract (Viscum album L.).

Lymphocytes of 25 patients treated with an aqueous mistletoe extract (Viscum album L.) for up to 6 months (group 1), up to 2 years (group 2), and more than 2 years (group 3) were examined in 3- and 7-day cultures for specifically sensitized lymphocytes. The whole extract (HM), the lectin-polysaccharide fraction (HM-LP), and the 'viscotoxin' fraction (HM-V) were added at concentrations ranging from 0.5 micrograms to 12.5 mg extract/ml. Lymphocytes from four of the nine group 2 patients and five of the ten group 3 patients reacted specifically with HM and HM-LP at an optimal dose of 5.0 mg/ml, but did not react with HM-V. Stimulation indices varied between 1.6 and 16. In the patients of group 3 this effect was observed only when their lymphocytes were co-stimulated in the 3-day cultures with phytohemagglutinin (PHA), in contrast to the four patients of group 2 who reacted only in the 7-day cultures with HM-LP without PHA co-stimulation. Patients' lymphocytes had to be protected from mistletoe lectin-induced cytotoxicity by the addition of their own sera containing anti-mistletoe lectin antibodies. Lymphocytes from tumor patients (n = 18) never treated with mistletoe extracts and healthy individuals (n = 18) showed no specific proliferative response when tested in 3- and 7-day cultures.(ABSTRACT TRUNCATED AT 250 WORDS)