Final answer:
The process where infected cells cross the blood-brain barrier is known as transcytosis, which involves the cells moving across the endothelial cells potentially within vesicles. The correct option is 3) Transcytosis
Step-by-step explanation:
The process by which infected cells migrate across the blood-brain barrier (BBB) can be encompassed by multiple mechanisms, including transcytosis and leukocyte-facilitated entry.
However, considering the choices provided, the most applicable term for the process where cells, including infected ones, cross the BBB is transcytosis. This involves the movement of cells across the endothelial cells of the BBB, potentially within vesicles. It is a type of endocytosis and can also involve exocytosis on the opposite side of the barrier.
The other terms listed are related processes: endocytosis is the engulfment of material into a cell by the inward folding of the cell membrane, exocytosis is the release of substances from a cell, and phagocytosis is a form of endocytosis where large particles, such as pathogens, are engulfed by cells like phagocytes. The correct option is 3) Transcytosis