A lectin from Chinese mistletoe increases γδ T cell-mediated cytotoxicity through induction of caspase-dependent apoptosis

In this study, a mistletoe lectin (ML) was purified from Chinese mistletoe and the effect of this 60 kDa Chinese ML on human gamma delta T cell cytotoxicity, apoptosis and modulation of the cytokine network was studied. The cytotoxic properties of delta T cells was evaluated by using a Cr-51 release test and employed fluorescence-activated cell sorting and enzyme-linked immunosorbent assay analysis to quantify translocation of the cell membrane phospholipid, phosphatidylserine and nuclear DNA fragmentation during apoptosis. It was found that: (i) ML effectively stimulated gamma delta T cell proliferation in a dose- and time-dependent manner; (ii) ML increased gamma delta T cell cytotoxicity; (iii) ML could modulate lipopolysaccharide-induced cytokine release in a pro-inflammatory manner by increasing tumor necrosis factor (TNF)-alpha release and inhibiting the release of anti -inflammatory interleukin (IL)-10; (iv) ML induced apoptosis in caspase-dependent and CD95-independent manner. The results indicated that ML is a potent immunomodulator to human gamma delta T cell cytotoxicity, apoptosis and cytokine production.