Stage-specific production of S-antigens of Plasmodium falciparum in vitro.

Stage-specific synthesis and release of the S-antigen of Plasmodium falciparum was demonstrated using 3H-glycine-labelled, synchronous, cloned parasite populations. The release of S-antigens into culture supernatants was first evident 25 to 30 hours after initiation of the parasite cycle and correlated with the rupture of the most mature schizonts. S-antigen release reached a peak at 37 to 43 hours at the height of the reinvasion cycle. Intracellular production of S-antigens was evident slightly earlier (19 to 24 hours) and correlated with the initial appearance of schizonts.