Lewis(x)-containing oligosaccharide attenuates schistosome egg antigen-induced immune depression in human schistosomiasis.

The proliferative and interleukin (IL)-10 responses to Lacto-n-fucopentaose III (LNFPIII) that contains Lewis(x)(Le(x))-trisaccharide was assessed in PBMC from humans infected with Schistosoma mansoni. All patient groups with low, medium, and high egg counts in their feces responded to polyvalent LNFPIII-HSA (where HSA = human serum albumin) conjugate. PBMC of all subjects showed a significant proliferative response to this sugar conjugate. However, the levels of interleukin (IL)-10 induced by LNFPIII-HSA were higher in groups with low and medium egg counts than those with high egg. Soluble egg antigens (SEA) also induced IL-10 production by PBMC from infected patients. Interestingly, the SEA-induced IL-10 production was remarkably inhibited by pretreatment of PBMC with free ligands of LNFPIII (monovalent form). These LNFPIII-pretreated PBMC displayed appreciable increase in the level of proliferation to SEA stimulation. We propose that the observed bystander immune potentiation rendered by free LNFPIII is due to the reduced IL-10 level which, presumably, up-regulate expression of co-stimulatory molecules on APC. The ensemble of results indicates that the Le(x)-containing LNFPIII is a potent immunoreactive epitope in SEA that negatively influences PBMC response against this parasite antigens via IL-10.