Thymocyte proliferation and maturation in response to galactoside-specific mistletoe lectin-1

Commercially available mistletoe extract standardized for the galactoside-specific mistletoe lectin-1 (ML-1) could be shown to induce thymocyte proliferation and maturation in BALB/c-mice after regular subcutaneous administration of the optimal immunomodulating dosage (1ng lectin/kg body weight). The increase in thymocyte numbers per mg organ weight was statistically significant. Determinations of thymic lymphatic subsets revealed considerable up-regulation of mature cells expressing helper/inducer (L3T4) or cytotoxic/suppressor (Lyt-2) phenotype and immature cells presenting both (L3T4/Lyt-2) antigens. Thus, administration of ML-1 accelerated murine thymocyte proliferation and maturation. Counts of BALB/c-mouse peripheral blood lymphocytes (PBL) revealed evident (but statistically non-significant) increases after ML-1 administration. The determination of activated PBL expressing interleukin (Il)-2 receptors proved, however, that ML-1 induced a potent immunostimulation since these cells were significantly enhanced after ML-1 administration.