Oxygen free radical and nitric oxide production in single or combined human schistosomiasis and fascioliasis.

The levels of superoxide (O(-)2) and nitric oxide (NO) production by monocytes have been measured in 15 patients with S. mansoni, 15 patients with Fasciola and six patients with combined infection as well as in control group (15). The levels of both radicals were significantly higher in all patient groups than in the control group, indicating that these radicals may have a role in the immunity against such infections. Patients with chronic fascioliasis showed lower level of O(-)2 and NO than those with schistosomiasis. This may be due to the lodging of the mature Fasciola spp. away from the immune system and subsequently decreased amount of antigens reaching the circulation. In combined infection, the levels of these products were at the highest value, due to increased antigenic stimulation and cross reactivity between the two parasites which may have lead to augmented immune response.