T lymphocyte interferon-gamma production induced by Plasmodium falciparum antigen is high in recently infected non-immune and low in immune subjects

Abstract

SUMMARY: Interferon (IFN) alpha and gamma were measured by radio-immunoassays in supernatanls fromcultures of peripheral blood mononuclear cells (PBMC) or purified T cell subsets incubated witheither Plasmodium falciparum schizonl-enriched malaria antigen (mAg). uninfected red blood cells(RBC) or pokeweed mitogen (PWM). Cell donors were 24 clinically immune, healthy African adultnative residents of a P. falciparum-endemic region, Haut-Ogooué, Gabon, and seven non-immune. European temporary residents with a history of a single to a few malaria infections during theprevious 1 to 9 months. When PBMC were cultured in medium alone or with RBC antigen no or lowtitres of IFN-γ were detected. PBMC proliferation and IFN-γ production observed in the presence ofmAg were dose dependent and significantly correlated. When cultured with mAg. PBMC from non-immune Europeans produced significantly higher levels of IFN-γ than did PBMC from clinicallyimmune Africans. No such difference was found when PBMC were cultured with PWM. The mAg-induced IFN-γ production was due mainly to CD4+ T cells and was not enhanced by CDS+ T celldepletion. No IFN-α was detected in culture supernatants. Thus. P. falciparum antigens are able toinduce in vitro production of IFN-γ by CD4+ Tcells; however, in this sample, individuals consideredlo be clinically resistant to malaria were low producers of IFN-γ.