Comparative studies on surface phenotypes of Theileria lestoquardi and T. annulata schizont-infected cells

Phenotypes of sheep cell lines infected with Theileria lestoquardi or T. annulata were studied by flow cytometric analysis, following immunolabelling with a panel of monoclonal antibodies reacting to leukocyte differentiation antigens. Cell surface phenotypes of Theileria-infected sheep cell lines derived ex vivo and in vitro were compared, both with each other and with cell lines from cattle undergoing acute T. annulata infection. Besides the non-lineage specific markers CD45, MHC class I and MHC class II, myeloid lineage-associated antigens and B cell-specific markers were expressed in all five different types of line, suggesting that both T. lestoquardi and T. annulata had infected the same cell types in sheep as T. annulata in cattle, notably monocytes/macrophages and B cells. Lineage-specific markers were generally expressed at low frequency and intensity; any differences between the five types of cell lines were quantitative, rather than qualitative. Thus, relative rather than absolute differences in cell preference of sporozoites of T. lestoquardi and T. annulata may contribute to the differences observed in previous studies in the course of the infection of sheep with each of these two parasites and in the infection of cattle with T. annulata.