Cornea transplant in humans is almost never rejected. This is because
- it is composed of enucleated cells
- it is a non-living layer
- its cells are least penetrable by bacteria
- it has no blood supply
Answer
(4) it has no blood supply
Solution
Graft rejection is brought about by the immune cells (lymphocytes) and antibodies that reach the graft through blood.
The cornea is avascular, i.e., it has no blood supply; it gets oxygen and nutrients by diffusion.
Immune cells cannot reach the transplanted cornea, so it is almost never rejected.
Answer: (4)