Here we show that in the chronic helminth infection onchocerciasis (river blindness), where patients have relatively little sign of dermatitis despite the presence of millions of small worms in the skin, T cells can be obtained which bear characteristics of Tr1 cells, producing no IL-2 or IL-4 but substantial amounts of IL-10, variable amounts of IL-5, and some IFN-gamma.
Induction of IL-5 at the mRNA level and IL-5 and IL-10 at the protein level was demonstrated in patients with the generalized form of onchocerciasis and endemic normals without clinical manifestations.
Furthermore, spontaneous production of high levels of IL-10 in onchocerciasis patients is likely to suppress Th1-type immunity, and thus may favour manifestation of chronic onchocerciasis.