Schistosoma haematobium in a Gambian community. II. Impaired cell-mediated immunity and other immunological abnormalities.

A decreased response rate in delayed hypersensitivity reactions was found in a population heavily infected with Schistosoma haematobium. Laboratory studies showed a depressed response of lymphocytes to PHA in infected subjects. Together these findings suggest the presence of a defect in cell-mediated immunity in some infected subjects. IgG and IgM levels were increased and the prevalence of rheumatoid factor was greater in the infected population. The possibility of non-specific changes in the control of the immune system in schistosome infections and the relation of the present findings to the increased prevalence of lymphoproliferative tumours in infected subjects are discussed.