Immune System's Role in Transplant Rejection

Steps:

• Identify that transplant rejection involves the body's defense mechanism attacking foreign tissue.
• Recall that the immune system uses specific cells to detect and respond to non-self antigens on transplanted tissue.
• Determine which blood component contains these immune cells responsible for recognition and attack.
• Link the process to cellular immunity, where mismatched tissues trigger a response leading to rejection.

Why D is correct:

• White blood cells, particularly lymphocytes (T-cells and B-cells), recognize foreign MHC antigens on transplant tissue and mount an immune response, as defined in immunology by the adaptive immune system's antigen-specific attack.

Why the others are wrong:

• A. Plasma carries antibodies but does not initiate cellular rejection; it's involved in humoral immunity only after activation.
• B. Platelets aid clotting, not immune surveillance or tissue rejection.
• C. Red blood cells transport oxygen and lack immune recognition capabilities.

Final answer: D