Intact glycans from cestode antigens are involved in innate activation of myeloid suppressor cells

During helminthic infections, strong Th2 type-biased responses concomitant with impaired cell-proliferative responses to parasitic and unrelated antigens are major immunological hallmarks. Parasite glycan structures have been proposed to play a role in modulating these responses. To understand early events related to immune modulation during cestode infection, we have examined the role of intact glycans of antigens from Taenia crassiceps in the recruitment of innate cells. Soluble antigens from this cestode contained higher levels of carbohydrates than proteins. Intraperitoneal injection of the antigens rapidly recruited a cell population expressing F4/80(+)/Gr-1(+)surface markers, which adoptively suppressed naïve T-cell proliferation in vitro in response to anti-CD3/CD28 MAb stimulation in a cell-contact dependent manner. Soluble antigens with altered glycans by treatment with sodium periodate significantly reduced the recruitment of F4/80(+)/Gr1(+)cells, concomitantly their suppressive activity was abrogated, indicating that glycans have a role in the early activation of these suppressor cells. Using C3H/HeJ and STAT6-KO mice, we found that expansion and suppressive activity of F4/80(+)Gr1(+)cells induced by T. crassiceps intact antigens was TLR4 and Th2-type cytokine independent. Together with previous studies on nematode and trematode parasites, our data support the hypothesis that glycans can be involved on a similar pathway in the immunoregulation by helminths.