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

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.