Mosquito injection of Plasmodium sporozoites into the bloodstream is followed by a short transit period before invasion of the hepatocyte, the only host cell expressing class I major histocompatibility complex (MHC) molecules. Liver stages develop within the hepatocyte for periods that vary according to the species, and they express various stage-specific proteins. Finally, schizonts are released into the bloodstream and invade the red blood cells, the final host cell before the continuation of the parasite cycle upon a subsequent mosquito bite.