A transplant can replace damaged or missing tissue, but the recipient’s immune system may recognize a graft as foreign and attack it. Understanding graft types and the role of human leukocyte antigens (HLAs) helps explain why some transplants are more likely to succeed than others.
A graft is tissue or an organ transplanted to another location to replace missing or damaged tissue. The graft must establish new connections with its blood supply and surrounding tissues.
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What is a graft?
A graft is tissue or an organ transplanted to a different location to replace missing or damaged tissue. It must establish connections with its blood supply and surrounding tissues.
How do an allograft and a xenograft differ?
An allograft is transferred between genetically distinct individuals of the same species. A xenograft is transferred between different species, such as from an animal to a human.
What are HLAs, and why do they matter in transplantation?
Human leukocyte antigens are human MHC molecules that help immune cells distinguish self from non-self. Differences between donor and recipient HLAs can contribute to recognition of the graft as foreign and trigger rejection.
How do T cells help reject a graft?
Cytotoxic T cells can kill graft cells directly. Helper T cells can release cytokines that activate macrophages, which can also damage graft tissue.
What is one benefit and one risk of immunosuppressant drugs?
They reduce immune attacks on a graft, but they also weaken defenses against infections and can increase the risk of transplant-related malignancies.
Quiz questions
What is an autograft?Answer: Tissue moved within the same person's body.
Which type of graft is transferred between genetically distinct individuals of the same species?Answer: A graft between genetically distinct members of one species.
How can recipient dendritic cells contribute to graft rejection?Answer: They process donor material and present it to recipient T cells.
Why may a parent or sibling be a suitable organ donor?Answer: Close relatives are more likely to share HLA alleles with the recipient.
Why can a transplant recipient remain vulnerable to infections while taking immunosuppressants?Answer: Reduced immune activity can also weaken defenses against infectious agents.
Based on Microbiology by Nina Parker, Mark Schneegurt, Anh-Hue Thi Tu, Philip Lister, Brian M. Forster (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.