Histocompatibility Principles Flashcards

What does histocompatibility refer to?

Answer: Tissue compatibility for transplants

Histocompatibility refers to the degree of similarity between the tissues of a donor and a recipient, which is critical for successful organ or tissue transplantation. A high degree of histocompatibility minimizes the risk of the recipient's immune system recognizing the transplanted tissue as foreign and rejecting it.

Which molecule plays a central role in histocompatibility?

Answer: HLA

Human Leukocyte Antigens (HLAs) are proteins found on the surface of most cells in the body, playing a vital role in the immune system's ability to distinguish self from non-self. These highly polymorphic molecules are the primary determinants of tissue compatibility, making them central to histocompatibility and transplant success.

Why is HLA typing necessary before transplantation?

Answer: To identify compatible tissue

HLA typing is essential before transplantation to match the donor and recipient as closely as possible based on their HLA profiles. A good HLA match significantly reduces the likelihood of the recipient's immune system mounting a strong rejection response against the transplanted organ or tissue, thereby improving transplant survival rates.

What is the function of the major histocompatibility complex (MHC)?

Answer: Present antigens to immune cells

The Major Histocompatibility Complex (MHC) molecules, which include HLAs in humans, are responsible for presenting fragments of proteins (antigens) to T lymphocytes. This presentation is crucial for the immune system to recognize foreign invaders (like pathogens) or abnormal cells, initiating an immune response.

Which cells are primarily involved in recognizing histocompatibility antigens?

Answer: T lymphocytes

T lymphocytes, specifically helper T cells and cytotoxic T lymphocytes, are the primary immune cells responsible for recognizing histocompatibility antigens presented by MHC molecules. They play a critical role in mediating cellular immunity and are key players in transplant rejection if the donor and recipient tissues are not compatible.

What type of rejection occurs within minutes of transplant due to preformed antibodies?

Answer: Hyperacute rejection

Hyperacute rejection is a severe and immediate form of transplant rejection that occurs within minutes to hours after transplantation. It is caused by pre-existing antibodies in the recipient's blood that recognize donor antigens, leading to rapid destruction of the transplanted organ.

Which technique is commonly used to detect HLA antibodies?

Answer: ELISA

Enzyme-Linked Immunosorbent Assay (ELISA) is a widely used laboratory technique to detect and quantify antibodies, including HLA antibodies, in a patient's serum. This method is crucial for pre-transplant screening to assess the recipient's sensitization status and identify potential risks of rejection.

Which test determines lymphocyte cytotoxicity in transplantation?

Answer: CDC assay

The Complement-Dependent Cytotoxicity (CDC) assay is a traditional method used in histocompatibility testing to detect HLA antibodies and perform crossmatching. It determines if a recipient's serum contains antibodies that can kill donor lymphocytes in the presence of complement, indicating a risk of rejection.

Which organization accredits histocompatibility laboratories in the U.S.?

Answer: ASHI

The American Society for Histocompatibility and Immunogenetics (ASHI) is the primary organization that provides accreditation for histocompatibility and immunogenetics laboratories in the United States. ASHI accreditation ensures that laboratories meet stringent quality standards and proficiency requirements for testing critical to organ transplantation.