Cornea transplant in humans is almost never rejected.This is because

Options

A. It is a non-living layer
B. Its cells are least penetrable by bacteria
C. It has no blood supply
D. It is composed of enculeated cells

Answer

**Step-by-Step Solution:**

1. **Understanding the Cornea**: The cornea is the transparent front part of the eye that covers the iris, pupil, and anterior chamber. It plays a crucial role in focusing light onto the retina.

2. **Characteristics of the Cornea**: The cornea is avascular, meaning it does not contain blood vessels. This is an important characteristic that affects its compatibility during transplants.

3. **Immune Response Mechanism**: In the human body, the immune system uses blood cells, particularly B and T lymphocytes, to identify and attack foreign tissues. These cells circulate through the bloodstream and are responsible for the rejection of transplanted organs.

4. **Reason for Low Rejection Rates**: Since the cornea has no blood supply, there are no B and T lymphocytes present in this area. This absence means that the immune system does not recognize the transplanted cornea as foreign, leading to a significantly reduced chance of rejection.

5. **Conclusion**: Therefore, the reason cornea transplants are almost never rejected is primarily due to the lack of blood supply, which prevents the immune response that typically leads to rejection of foreign tissues.

**Final Answer**: The correct answer is that the cornea has no blood supply.

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