Soluble plasma IL-2 receptors and malaria

Plasma levels of soluble IL-2 receptor (sIL-2R) were measured by immunoassay in 180 individuals, aged 1-70 years, living in a malaria-endemic community in West Africa. sIL-2R levels were compared with age, malaria parasitaemia, malaria-associated morbidity and cellular immune responses to Plasmodium falciparum antigens. Plasma levels of sIL-2R were independently associated with both age and patent malaria parasitaemia. No significant association was observed between IL-2R levels and concurrent malaria morbidity (i.e. fever associated with malaria), but the number of individuals with clinical malaria at the time of sampling was small. Although there was no association between plasma sIL-2R levels and in vitro proliferative responses of peripheral blood mononuclear cells (PBMC) to a number of defined malaria antigens, we did find a significant negative association between sIL-2R and in vitro proliferation of unstimulated PBMC. High levels of sIL-2R (up to 5500 U/ml) were detected in the plasma of malaria-infected individuals; this is indicative of a vigorous cellular immune response to malaria antigens in vivo and does not support the notion that malaria infections are generally immunosuppressive. Indeed, we found that, at the low levels of parasitaemia present in study subjects, there was no significant difference in the mean proliferative response to malaria antigens in infected subjects when compared with uninfected subjects.