To determine the immunomodulatory effects of lentinan, particularly on immune-suppressing regulatory T cells (Treg), in a mouse model of malaria, BALB/c mice were infected with Plasmodium yoelii by intraperitoneal (i.p.) injection of 1 × 10 6 red blood cells containing Py17XL, and the infected mice were randomized into either a control group for i.p. injection of PBS or an experiment group for i.p. injection of lentinan. The results show that mean survival was significantly longer for infected

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... ice treated with lentinan (8.10 ± 2.53 days) than for infected controls treated with PBS (5.20 ± 1.20 days; P<0.01). Further, IL-12 and IFN-γ γ γ γ expression in spleen cells were significantly higher in the experiment group than the control group (P<0.01). When Treg cells were isolated by CD antibody detection from peripheral blood, a higher proportions were undergoing apoptosis in the experiment group than those in the control group (P<0.001). To determine the mechanism of cell death in Tregs, we analyzed Bax and Bcl-2 expression. Bax was detected at significantly higher levels, while Bcl-2 was significantly lower in Treg cells from lentinan-treated animals (P<0.001). In conclusion, lentinan significantly delayed progression of P. yoelii infection in mice by up-regulating anti-inflammatory cytokines and triggering apoptosis of Treg cells through up-regulation of Bax and down-regulation of Bcl-2, and which should be suggested in the clinical experience in the future.