Occurrence of S-antigens in serum in Plasmodium falciparum infections in man.

Gambians with severe Plasmodium falciparum infections frequently have malarial S-antigens in their serum or plasma. Detection of these with the available antisera which are from immune adults is complicated because there are many different S-antigens and none of the antisera contains antibodies to them all. Despite this we found S-antigens in about 60% of a large series of malarious children and demonstrated that this was a considerable underestimate of the true incidence. We also showed that the prevalence of S-antigens was related to the malaria season and to the intensity of infection.