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(A) After attachment to a host cell, T. gondii secretes lipids (red) from internal organelles. After invasion, the parasite replicates in the special vacuole formed from parasite lipids. This vacuole lacks the host cell proteins associated with normal endosomes, and the parasitic vacuole does not fuse with lysosomes. After several rounds of replication, the parasite causes the host cell to lyse, and progeny are released to infect other host cells. (B) Light micrograph of T. gondii replicating in a vacuole in a cultured cell. (B, courtesy of Manuel Camps and John Boothroyd.)