(a).

Source	Year	Transplants			Recipients
		Species	Strain	Tissue used	Species	Strain	Location
Nicholas et al. [40]	1987	Mice	BALB/cANC	Embryonic neocortex These cells do not express MHC I.	Mice	BALB/cANC 6–8-week-old female mice	Right lateral ventricle
			CBA/J
			E15–18
		Results
		Significantly more inflammatory cells in allogeneic than in syngeneic grafts. There were some T cells in the allogeneic grafts, but not syngeneic grafts. More neurons survive in syngeneic versus allogeneic grafts. There is less necrosis as well.
Lawrence et al. [41]	1990	Rat	PVG	Embryonic hippocamus	rat	AO	Hippocampus
			AO	(E18–20)-no MHC I
		Results
		Allografts were rejected by both macrophages and cytotoxic T cells. Grafts were infiltrated early (3–6 d) by host microglia especially in necrotic tissue surrounding the graft. Blood vessels begin to join the graft to the host as early as 1 day. Lymphocytes, macrophages, and microglia begin to accumulate around the larger vessels. MHC I expression is turned on 3–6 days after transplanting. Most cells in the allografts were rejected by cytotoxic T cells by 27 d.