Acquired immunity and reinfection with Schistosoma japonicum. III. Study of the association between cytokine production by peripheral blood mononuclear cells in vitro and resistance to Schistosoma japonicum infection in residents from an endemic area

Sixty-seven residents of an area of China endemic for schistosomiasis (Schistosoma japonicum) were divided into 3 groups. The first was resistant (with high exposure level and negative stool for schistosome eggs; n=21), the 2nd was susceptible (positive stool; n=16) and the 3rd was indeterminate (with lower exposure level and negative stool; n=30). Peripheral blood mononuclear cells (PBMCs) from these subjects and from individuals residing in a non-endemic area (control group) were incubated in the presence of adult worm antigen (AWA), or 5 recombinant S. japonicum antigens. Cytokines (IL-5, IL-10 and IFN-γ) were determined quantitatively by sandwich-ELISA using cytokine-specific monoclonal antibodies. Following stimulation with AWA, PBMCs from individuals from the endemic area produced significantly higher levels of IL-5, IL-10 and IFN-γ than did those from controls. When PBMCs were incubated in the presence of one of the 5 recombinant schistosome antigens, only IL-10 production differed significantly between the endemic and non-endemic groups. Following stimulation by TegAg, FABP or GAPDH, PBMCs from individuals of the resistant group produced markedly higher levels of IL-10 than did those from the susceptible group. Following stimulation by GST [glutathione S-transferase], levels of IFN-γ in supernatants of PBMCs from resistant individuals were significantly higher than those of PBMCs from susceptible individuals. No direct evidence of a relationship between cytokine production and exposure levels was observed.