MODULATION OF THE CELLULAR IMMUNE-RESPONSE DURING PLASMODIUM-FALCIPARUM INFECTIONS IN SICKLE-CELL TRAIT INDIVIDUALS

Plasma and peripheral blood mononuclear cells (PBMC) were obtained fro m P. falciparum-infected individuals with and without the sickle cell trait at diagnosis and 7 days after treatment. HbAA and HbAS patients were compared for levels of plasma soluble IL-2 receptors (IL-2R) and the in vitro cellular reactivity to affinity-purified soluble P. falci parum antigens (SPAg), PPD and phytohaemagglutinin (PHA). At diagnosis , HbAS patients with clinical disease had lower plasma-soluble IL-2R l evels and parasite counts than the corresponding HbAA patients, wherea s HbAS and HbAA patients with asymptomatic infections had comparable s oluble IL-2R levels and parasite counts. PBMC from HbAS patients had h igher proliferation and IFN-gamma production in response to SPAg than PBMC from HbAA patients. The difference in the lymphoproliferative res ponses to SPAg between the two groups was evident in patients with asy mptomatic infections. In all patients, the clinical severity, the solu ble IL-2R levels and the parasite counts were directly related. The fo rmer two were inversely related to the proliferative responses to SPAg . After treatment, all the studied parameters were comparable in the t wo groups. The study indicates that during P. falciparum infection, Hb AS compared with HbAA patients had lower in vivo cellular activation a nd higher in vitro cellular reactivity in response to soluble malaria antigens.