Identification of the lipid mediator prostaglandin E2 in tissue immune cells of humans infected with the filaria Onchocerca volvulus

Prostaglandins generated by multiple tissue and immune cells exhibit regulatory effects on the vascular and immune systems. Prostaglandin E2 (PGE2), in particular, affects innate as well as adaptive immune mechanisms. We identified PGE2 in host immune cells adjacent to Onchocerca volvulus in subcutaneous onchocercomas and the affected skin. Using immunohistology, PGE2 was predominantly detected in infiltrating macrophages but also in plasma cells. Consecutive sections revealed concomitant presence of PGE2 and transforming growth factor-beta (TGF-beta), representing a second immunoregulative mediator in macrophages and plasma cells. TGF-beta was preferentially observed in the infiltrating macrophages in patients with a generalized hyporeactive onchocerciasis and less in patients with the hyperreactive form. The presence of PGE2 and TGF-beta in adjoining host cells infiltrating in the onchocercoma and dermis may indicate containment of inflammatory responses that could favour survival of the filarial parasite.