Blood Typing and Matching PDF - Pearson

BLOOD TYPING AND MATCHING Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Blood transfusions—blood taken from donor is given to recipient; commonly used treatment modality in today’s medicine, but was not always case – Discovery of surf...

BLOOD TYPING AND MATCHING Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Blood transfusions—blood taken from donor is given to recipient; commonly used treatment modality in today’s medicine, but was not always case – Discovery of surface markers or antigens found on most biological molecules and all cells, including erythrocytes; lead to development of safer transfusion practices ▪ Immune system recognizes foreign antigens; responds by trying to remove them ▪ Response was responsible for many fatalities in early-era transfusion patients – Antigens on erythrocytes (genetically determined carbohydrate chains) give rise to different blood groups – Two groups of 30 different antigens found on erythrocytes are particularly useful for clinical use: ABO blood group and Rh blood group Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Typing ABO blood group features two antigens, A and B antigens; gives rise to four ABO types: Type A—only A antigen is present on erythrocytes Type B—only B antigen is present on erythrocytes Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Typing ABO blood groups (continued): Type AB—both A and B antigens are present on erythrocytes Type O—neither A nor B antigens are present on erythrocytes; there is no O antigen; O denotes absence of A and B antigens only Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Typing Rh blood group features Rh antigen first discovered in rhesus monkeys; individuals with Rh antigen (D antigen) on their erythrocytes are Rh-positive (Rh+) and those without D antigen are Rh-negative (Rh−) ABO and Rh blood groups combined give rise to eight common blood types Type O+ is most common blood type in US populations, while AB− is least common Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Typing Blood typing in laboratory uses antibodies that bind to individual antigens on erythrocytes – Antibodies (called agglutinins) bind to surface-bound antigens; cause them to clump together or agglutinate – Ultimately, agglutination promotes erythrocyte destruction; called hemolysis Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Typing Blood sample is treated with three different antibodies; agglutination indicates that antigen is present on erythrocytes; no agglutination indicates that specific antigen is absent; antibodies used: – Anti-A antibodies bind and agglutinate A antigens – Anti-B antibodies bind and agglutinate B antigens – Anti-Rh (Anti-D) antibodies bind and agglutinate Rh antigens Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Typing Blood samples from four patients are combined with antibodies. Agglutination indicates that a specific antigen is present on that patient’s erythrocytes. Figure 19.19 Blood type testing. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Immune system recognizes antigens on erythrocytes as “self ” antigens; does not produce antibodies to self antigens, because if it did, antibodies would bind own antigens Immune system does produce antibodies to foreign antigens; means that antibodies are present in plasma only if antigens are absent from erythrocytes Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Note that anti-A and anti-B antibodies are pre-formed; they are present in plasma even if individual has never been exposed to those antigens Anti-Rh antibodies, however, are produced only if person has been exposed to blood containing Rh antigens Therefore, an Rh− individual generally has no anti-Rh antibodies unless he or she has been exposed (sensitized) to Rh+ erythrocytes Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Antigens and antibodies are basis for blood matching; blood taken from donor is screened for compatibility prior to its administration to recipient – Patients cannot receive any blood containing antigens that his/her immune system would recognize as foreign – Match occurs if donor blood type is compatible with recipient blood type – Transfusion reaction—recipient antibodies bind to donor antigens; causes agglutination that destroys donor erythrocytes, possibly leading to kidney failure and death Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Figure 19.20 Matching blood types for blood transfusions. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Universal donor—Blood type O− – Erythrocytes do not have A, B, nor Rh surface antigens – Can be given to any other blood type in emergency when blood matching is not option Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Universal recipient—blood type AB+ – These individuals do not make antibodies to A, B, or Rh antigens – Individuals with AB+ blood type can generally receive blood from any blood type donors – Matching is still safest practice Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Blood Transfusions Table 19.4 The Eight Major Blood Types. Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Concept Boost: What about the Donor’s Antibodies? Donor antibodies can bind to recipient’s antigens, and unless blood types are exactly matched, some donor antibodies might destroy few recipient’s erythrocytes – Key word is few—only a few of recipient’s erythrocytes are likely to be harmed – Take a closer look at example in Figure 19.20a Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved Hemolytic Disease of the Newborn Also known as erythroblastosis fetalis; occurs when Rh− mother gives birth to Rh+ fetus During birth fetal RBCs enter mother’s blood; stimulates her immune system to produce anti-Rh antibodies First pregnancy is not typically at risk; in subsequent pregnancies maternal anti-Rh antibodies can cross placenta and hemolyze Rh+ fetal RBCs Effectively prevented with blood type screening; if woman is Rh−, can be given Rho (D) immune globulin; contains anti-Rh antibodies that bind fetal cells in maternal circulation; prevents maternal production of anti-Rh antibodies Copyright © 2019, 2016 Pearson Education, Inc. All Rights Reserved