(b).

Source	Year	Transplants		Recipients			Number of cells
		Species	Cell type	Species	Strain	Location
Rémy et al. [50]	2001	Pig	Aortic endothelial cells from 30 d old pigs express both MHC I and MHC II	Rat	LEW.1A	Striatum	400,000
		Pig	Embryonic neurons from ventral mesencephalon e25–28 express little or no MHC I.				400,000
		Results
		Endothelial cells were rejected quickly (3–7 days) by primarily macrophage/microglia cells. Neurons were rejected much later (14–21 days) by both macrophages and cytotoxic lymphocytes.