The integrity of host lymphocyte plasmalemma during its invasion by Theileria annulata sporozoites as demonstrated by ruthenium red staining.

The integrity of host lymphocyte plasma membrane during its invasion by Theileria annulata sporozoites was examined in an in vitro system using ruthenium red staining. It was demonstrated that during interiorisation of the sporozoites, the dye was completely excluded from the intracellular milieu, indicating that the continuity of the host-cell plasmalemma was not disrupted throughout the process of penetration, and confirmed a previous observation that the fragmentation of the host lymphocyte membrane only occurs later, after the parasite is intracellular.