Why does the immune system attack a transplanted organ?

• A. Because the immune system is suppressed after transplantation
• B. Because the transplanted organ contains antigens that are recognized as foreign by the recipient's immune system
• C. Because the transplanted organ releases toxins that trigger an immune response
• D. Because the immune system is unable to distinguish between self and non-self cells

Answer: (B)

Verified step by step guidance

1. Understand that the immune system's primary function is to distinguish between self and non-self to protect the body from harmful invaders like pathogens.
2. Recognize that transplanted organs come from another individual and therefore carry different surface molecules called antigens, which are proteins or markers on the cells.
3. Know that these foreign antigens on the transplanted organ are detected by the recipient's immune system as non-self, triggering an immune response.
4. Realize that this immune response involves activation of immune cells that attack the transplanted organ to eliminate what they perceive as a threat.
5. Conclude that the immune system attacks the transplanted organ because it recognizes the organ's antigens as foreign, not because of toxins or immune suppression alone.