Q.86 Which one of the following tissues/organs is least likely to experience
graft rejection when transplanted from a person to an unrelated person?
(A) bone marrow
(B) cornea
(C) heart
(D) kidney

Cornea is the tissue least likely to experience graft rejection when transplanted from an unrelated donor. This makes it the correct answer (B) for the question, as its avascular nature limits immune cell access compared to vascularized organs or tissues like bone marrow. Understanding graft rejection mechanisms helps explain why cornea transplants succeed at rates over 90% even without HLA matching.

Option Analysis

Graft rejection occurs mainly due to T-cell recognition of foreign MHC antigens on donor cells, with vascularized tissues facing higher risks from blood-borne immune responses.

• Bone marrow (A): High rejection risk in unrelated transplants due to host-versus-graft reactions; graft failure rates reach 5-45%, plus graft-versus-host disease from donor immune cells.

• Cornea (B): Lowest rejection due to no blood vessels, minimizing antigen presentation; first-time success exceeds 90% at two years, even unrelated.

• Heart (C): Vascularized organ prone to acute rejection (17-30% at one year); requires lifelong immunosuppression.

• Kidney (D): Common rejection (6-10% acute at one year); HLA matching critical for unrelated donors.

Graft rejection in transplants from unrelated persons poses major challenges due to immune responses against foreign antigens. Cornea stands out as the tissue least likely to face graft rejection, thanks to its unique biology ideal for successful transplantation.

Immune Basis of Graft Rejection

Transplant rejection stems from T-cell activation against donor MHC molecules, strongest in vascularized tissues where blood delivers immune effectors. Avascular tissues evade this, explaining cornea’s advantage over bone marrow, heart, or kidney.

Why Cornea Succeeds Most

The cornea lacks blood vessels, blocking lymphocyte access and antigen presentation; its anterior chamber fosters immune privilege. Rejection rates stay low (10-20% even in at-risk cases), with 90%+ two-year survival unrelated.

Risks in Other Options

Bone marrow risks bidirectional rejection; heart and kidney need heavy immunosuppression.

CSIR NET Relevance

For exams like CSIR NET Life Sciences, note cornea’s immune privilege as key to low rejection, contrasting vascular organs—crucial for immunology questions.