What is the significance of the presence of MHC molecules on the surface of parasites in human neurocysticercosis?

Abstract

Sixteen cysticerci excised from 15 surgery patients were examined for the presence of HLA molecules on their surface, to confirm the role of these molecules in parasite damage and to investigate if HLA products are host specific or perhaps host-like antigens synthesized by the parasite. MoAbs against monomorphic and polymorphic HLA were chosen according to the patients HLA phenotypes. MoAbs against host and non-host antigens were selected and tested on cyst slides by indirect immunofluorescence assays. Host molecules were present in 43.7% of the cysts, but non-host antigens were also apparent in 62.5%. These results suggest mimicry as a possible mechanism to explain the presence of MHC products on the surface of the parasite; inflammation may also induce the expression of HLA that could become associated with the parasite. In vitro cellular immune response to specific antigens was also performed and positive responses correlated with the presence of HLA molecules on the cyst's surface. Moreover, damaged parasites had host molecules as well. Parasites from responder patients had all kind of HLA molecules or at least, antigenic determinants while the cysts from non-responders did not have molecules on their surface. These data support the role of HLA in cyst destruction.