Question

Chronic rejection mechanism in host vs graft is caused by

• A. CD4+ T cells
• B. Antibody
• C. CD8+ T cells
• D. Macrophages

Hint:

• Chronic Graft Rejection Slow, progressive loss of graft function over months/years.
• Involves both cellular (T cells, macrophages) and humoral (antibodies) immune mechanisms.
• Characterized by fibrosis, vascular damage (graft arteriosclerosis), and chronic inflammation.
• CD4+ T cells are critical in initiating and sustaining the alloimmune responses leading to chronic rejection.

Answer 1

The Correct Option is A

Chronic rejection in transplant scenarios, specifically in the context of host versus graft rejection, is primarily mediated by CD4+ T cells. Here's a detailed explanation of this mechanism:

1. Immune Response Activation: In a transplant, the recipient's immune system recognizes the transplanted organ or tissue as foreign. This response is triggered by the recognition of donor antigens by host immune cells.

2. Role of CD4+ T Cells: CD4+ T cells, also known as helper T cells, play a pivotal role in the immune response. They are activated when they encounter antigen-presenting cells (APCs) carrying the foreign antigens of the graft.

3. Cytokine Secretion: Once activated, CD4+ T cells secrete cytokines, which are signaling molecules that orchestrate the immune response. These cytokines help in recruiting and activating other immune cells, including CD8+ T cells, B cells, and macrophages.

4. Chronic Rejection Mechanism: Over time, the continued immune attack leads to inflammation and progressive damage to the graft tissues, known as chronic rejection. The process is characterized by fibrosis and vascular narrowing within the graft, primarily mediated by the cytokines released from CD4+ T cells.

5. Conclusion: While other immune cells like CD8+ T cells, antibodies, and macrophages are involved in the overall rejection process, it is the activation and function of CD4+ T cells that chiefly drive chronic rejection in host versus graft scenarios.