Eimeria Bovis Infection Enhances Adhesion of Peripheral Blood Mononuclear Cells to and Their Transmigration Through an Infected Bovine Endothelial Cell Monolayer in Vitro

The first schizogony of Eimeria bovis takes place in lymphatic endothelial cells of the ileum, resulting in the formation of macroschizonts within 2-3 weeks. In this study, we analyse early cellular immune responses to infected host cells on the basis of peripheral blood mononuclear cell (PBMC) adhesion on and transmigration through infected bovine umbilical vein endothelial cell (BUVEC) monolayers. Adhesion of PBMC was upregulated by an E. bovis infection. Most marked effects were observed 1 day p.i.; thereafter, PBMC adhesion declined reaching control levels from day 8 p.i. onward. CD8(+) T cells adhered more frequently to infected BUVEC (42%) than CD4(+) T cells (25%). About one third of attached PBMC were represented by gammadelta-TCR(+) T cells. Adhesion of T cells was not restricted to parasitised host cells, but occurred almost equally on non-infected BUVEC within the same monolayer. Furthermore, we found moderately enhanced levels of PBMC transmigration through infected BUVEC monolayers, in particular on day 2 p.i. The data presented here suggest that E. bovis infection of BUVEC induces endothelial cell-derived proinflammatory reactions, which appear suitable for the initiation of both adaptive and innate immune responses.