Modulating activity of mistletoe lectins 1 and 2 on the lymphatic system in BALB/c-mice

The galactoside-specific lectin (mistletoe lectin-1, VAA-1) and the N-acetylgalactosamine-specific lectin (mistletoe lectin-2, VAA-2) were purified from aqueous mistletoe extract and checked for their immunoactive potency. Regular subcutaneous administration of the optimal immunomodulating VAA-1 /VAA-2 dosage (1 ng lectin/kg body weight) could be shown to modulate thymocyte proliferation, maturation, emigration and activation in BALB/c-mice. Thus, the increase in thymocyte counts was statistically significant after VAA-1 treatment. However, analogue VAA-2 applications significantly decreased thymocyte proliferation. Determinations of lymphatic subsets revealed considerable upregulation (after VAA-1 treatment) and significant downregulation (after VAA-2 treatment) of immature L 3 T4(+)/Lyt-2(+) thymic cells. Counts of mature cells expressing helper/inducer (L3T4(+)) or suppressor/cytotoxic (Lyt-2(+)) phenotypes did not present remarkable differences after VAA-1/VAA-2 administration. Counts of BALB/c-mouse peripheral blood cells revealed evident (statistically non-significant) increases of lymphocytes (PBL) and monocytes (PBM) after VAA-1 treatment, however, cell counts after VAA-2 administration were comparable to non-treated control animals. The determination of activated PBL expressing interleukin IL-2 receptors proved that VAA-1 induced a potent immunostimulation, since these cells were significantly enhanced after VAA-1 administration but not after VAA-2 treatment.