Blast transformation of adherent macrophages infected in vitro with sporozoites of Theileria parva.

Rhipicephalus appendiculatus ticks were fed on cows with parasitemia from Theileria parva infection (East Coast fever). Homogenates of salivary glands with infective sporozoites were added to cultures of (i) monocyte-derived adherent macrophages from normal bovine peripheral blood and (ii) macrophages from spleen and bone marrow. It was shown by light, phase-contrast, and electron microscopies and by tests for lysosomal enzymes, phagocytosis of carbon particles, and cell markers (fibronectin and Fc receptors) that macrophages transformed in vitro to blast cells containing macroschizonts in 2 to 3 weeks. These blasts detached from the monolayer and grew indefinitely in suspension culture.