Four major blood types exist in the human ABO blood system: types A, B, AB, and O; and there are three alleles that code for them. The A and B alleles are codominant, and the O allele is recessive. Blood types are derived from the presence of specific polysaccharide antigens that lie on the outer surface of the red blood cell membrane. The A allele codes for the production of the A antigen; the B allele codes for the production of the B antigen; the O allele does not code for any antigen.While there are many other antigens found on red blood cell membranes, the second most important antigen is the Rh antigen. Rh is an autosomally dominant trait coded for by 2 alleles. If this antigen is present, an individual is Rh+; if it is absent, an individual is Rh-. For example, a person with type AB blood with the Rh antigen is said to be AB+.These antigens become most important when an individual comes into contact with foreign blood. Because of the presence of naturally occurring substances that closely mimic the A and B antigens, individuals who do not have these antigens on their red blood cells will form antibodies against them. This is inconsequential until situations such as blood transfusion, organ transplant, or pregnancy occur. Erythroblastosis fetalis is a condition in which the red blood cells of an Rh+ fetus are attached by antibodies produced by its Rh- mother. Unlike ABO incompatibility, in which there are naturally occurring antibodies to foreign antigens, the Rh system requires prior sensitization to the Rh antigen before antibodies are produced. This sensitization usually occurs during the delivery of an Rh+ baby. So while the first baby will not be harmed, any further Rh+ fetuses are at risk.The Coombs tests provide a method for determining whether a mother has mounted an immune response again her baby's blood. The tests are based on whether or not agglutination occurs when Coombs reagent is added to a sample. Coombs reagent contains antibodies against the anti-Rh antibodies produced by the mother. The indirect Coombs test takes the mother's serum, which contains her antibodies but no red blood cells, and mixes it with Rh+ red blood cells. Coombs reagent is then added. If agglutination occurs, the test is positive, and the mother must be producing anti-Rh antibodies. The direct Coombs test mixes the baby's red blood cells with Coombs reagent. If agglutination occurs, the test is positive, and the baby's red blood cells must have been attacked by its mother's anti-Rh antibodies.If a man with type AB blood needed a transfusion of red blood cells, which of the following individuals could safely donate blood?
Answer(s): D
The thinking process behind this question is similar to the one used to answer the previous question. A person with type AB blood expresses both the A and B antigens on his red blood cells, which implies that his blood does NOT contain any anti-A or anti-B antibodies. Since the recipient's blood does not contain anti-A antibodies or anti-B antibodies; this means that any blood type can b safely transfused, regardless of the A and B antigens found in the donor's blood. Be aware that there are other blood antigens typically present that could cause problems during transfusions, but this is beyond the scope of this question. Also recognize that the gender of the person donating the blood is in no way relevant.
Four major blood types exist in the human ABO blood system: types A, B, AB, and O; and there are three alleles that code for them. The A and B alleles are codominant, and the O allele is recessive. Blood types are derived from the presence of specific polysaccharide antigens that lie on the outer surface of the red blood cell membrane. The A allele codes for the production of the A antigen; the B allele codes for the production of the B antigen; the O allele does not code for any antigen.While there are many other antigens found on red blood cell membranes, the second most important antigen is the Rh antigen. Rh is an autosomally dominant trait coded for by 2 alleles. If this antigen is present, an individual is Rh+; if it is absent, an individual is Rh-. For example, a person with type AB blood with the Rh antigen is said to be AB+.These antigens become most important when an individual comes into contact with foreign blood. Because of the presence of naturally occurring substances that closely mimic the A and B antigens, individuals who do not have these antigens on their red blood cells will form antibodies against them. This is inconsequential until situations such as blood transfusion, organ transplant, or pregnancy occur.Erythroblastosis fetalis is a condition in which the red blood cells of an Rh+ fetus are attached by antibodies produced by its Rh- mother. Unlike ABO incompatibility, in which there are naturally occurring antibodies to foreign antigens, the Rh system requires prior sensitization to the Rh antigen before antibodies are produced. This sensitization usually occurs during the delivery of an Rh+ baby. So while the first baby will not be harmed, any further Rh+ fetuses are at risk.The Coombs tests provide a method for determining whether a mother has mounted an immune response again her baby's blood. The tests are based on whether or not agglutination occurs when Coombs reagent is added to a sample. Coombs reagent contains antibodies against the anti-Rh antibodies produced by the mother. The indirect Coombs test takes the mother's serum, which contains her antibodies but no red blood cells, and mixes it with Rh+ red blood cells. Coombs reagent is then added. If agglutination occurs, the test is positive, and the mother must be producing anti-Rh antibodies. The direct Coombs test mixes the baby's red blood cells with Coombs reagent. If agglutination occurs, the test is positive, and the baby's red blood cells must have been attacked by its mother's anti-Rh antibodies.How might one most practically assess the risk of erythroblastosis fetalis in a pregnant woman?
Answer(s): C
In answering this question, you must have an understanding of Rh incompatibility and also keep in mind that you're asked to choose the most PRACTICAL screening program. Rh incompatibility exists when an Rh negative mother, who has been sensitized to the Rh antigen by a previous pregnancy, is pregnant with another Rh positive baby. The risk exists in that the mother, as a result of this previous exposure to the Rh antigen, has produced antibodies that will now attack the fetus' red blood cells, which are Rh positive. So, the first step in making the assessment of erythroblastosis fetalis risk is to narrow down the group being assessed. Well, the mother must definitely be Rh negative for there to be ny risk at all, which means that testing all women, as a choice A, is extremely impractical. So choice A is incorrect. Choice B is incorrect because it tests all fetuses for the presence of the Rh antigen. This is useless unless the mother is known to be Rh negative. The most practical test is the one that singles our Rh negative mothers for testing. So, choice B is also incorrect. Choice C, however, is practical. It does single out Rh negative mothers to test them for the presence of anti-Rh antibodies. Choice D is not practical because all mothers of Rh positive children, regardless of their own blood type, are tested. Both Rh positive and Rh negative mothers would be tested, which is unnecessary and expensive. So, choice C is the correct answer; test Rh negative mothers to determine whether or not they are producing anti-Rh antibodies. If the test is positive, then there is a risk of erythroblastosis fetalis for an Rh positive fetus.
Four major blood types exist in the human ABO blood system: types A, B, AB, and O; and there are three alleles that code for them. The A and B alleles are codominant, and the O allele is recessive. Blood types are derived from the presence of specific polysaccharide antigens that lie on the outer surface of the red blood cell membrane. The A allele codes for the production of the A antigen; the B allele codes for the production of the B antigen; the O allele does not code for any antigen.While there are many other antigens found on red blood cell membranes, the second most important antigen is the Rh antigen. Rh is an autosomally dominant trait coded for by 2 alleles. If this antigen is present, an individual is Rh+; if it is absent, an individual is Rh-. For example, a person with type AB blood with the Rh antigen is said to be AB+.These antigens become most important when an individual comes into contact with foreign blood. Because of the presence of naturally occurring substances that closely mimic the A and B antigens, individuals who do not have these antigens on their red blood cells will form antibodies against them. This is inconsequential until situations such as blood transfusion, organ transplant, or pregnancy occur. Erythroblastosis fetalis is a condition in which the red blood cells of an Rh+ fetus are attached by antibodies produced by its Rh- mother. Unlike ABO incompatibility, in which there are naturally occurring antibodies to foreign antigens, the Rh system requires prior sensitization to the Rh antigen before antibodies are produced. This sensitization usually occurs during the delivery of an Rh+ baby. So while the first baby will not be harmed, any further Rh+ fetuses are at risk.The Coombs tests provide a method for determining whether a mother has mounted an immune response again her baby's blood. The tests are based on whether or not agglutination occurs when Coombs reagent is added to a sample. Coombs reagent contains antibodies against the anti-Rh antibodies produced by the mother. The indirect Coombs test takes the mother's serum, which contains her antibodies but no red blood cells, and mixes it with Rh+ red blood cells. Coombs reagent is then added. If agglutination occurs, the test is positive, and the mother must be producing anti-Rh antibodies. The direct Coombs test mixes the baby's red blood cells with Coombs reagent. If agglutination occurs, the test is positive, and the baby's red blood cells must have been attacked by its mother's anti-Rh antibodies.Based on information in the passage, what does the reaction below represent?
Answer(s): B
As described in the passage, the Coombs tests are the screening procedures used to assess whether an Rh incompatibility reaction can or has occurred. The direct Coombs test will identify whether the baby's red blood cells have in fact been attacked by the mother's anti-Rh antibodies. The indirect Coombs test tests for the presence of anti-Rh antibodies in the mother's serum. The figure in the question shows red blood cells with anti-Rh antibodies already attached to them, being mixed with Coombs reagent. This is the test described in the fourth paragraph of the passage as being the direct Coombs tests. Therefore, choices C and D can be eliminated. The outcome shows that Coombs reagent reacted with the red blood cells; the results of this test are therefore positive; so choice A is wrong and choice B is right. In order for either a direct or indirect Coombs test to be negative, the anti-Rh antibody cannot be present. For this to have been a positive indirect Coombs test, there would have been an additional, previous step showing the mixing of the mother's serum with washed red blood cells.
Four major blood types exist in the human ABO blood system: types A, B, AB, and O; and there are three alleles that code for them. The A and B alleles are codominant, and the O allele is recessive. Blood types are derived from the presence of specific polysaccharide antigens that lie on the outer surface of the red blood cell membrane. The A allele codes for the production of the A antigen; the B allele codes for the production of the B antigen; the O allele does not code for any antigen.While there are many other antigens found on red blood cell membranes, the second most important antigen is the Rh antigen. Rh is an autosomally dominant trait coded for by 2 alleles. If this antigen is present, an individual is Rh+; if it is absent, an individual is Rh-. For example, a person with type AB blood with the Rh antigen is said to be AB+.These antigens become most important when an individual comes into contact with foreign blood. Because of the presence of naturally occurring substances that closely mimic the A and B antigens, individuals who do not have these antigens on their red blood cells will form antibodies against them. This is inconsequential until situations such as blood transfusion, organ transplant, or pregnancy occur.Erythroblastosis fetalis is a condition in which the red blood cells of an Rh+ fetus are attached by antibodies produced by its Rh- mother. Unlike ABO incompatibility, in which there are naturally occurring antibodies to foreign antigens, the Rh system requires prior sensitization to the Rh antigen before antibodies are produced. This sensitization usually occurs during the delivery of an Rh+ baby. So while the first baby will not be harmed, any further Rh+ fetuses are at risk.The Coombs tests provide a method for determining whether a mother has mounted an immune response again her baby's blood. The tests are based on whether or not agglutination occurs when Coombs reagent is added to a sample. Coombs reagent contains antibodies against the anti-Rh antibodies produced by the mother. The indirect Coombs test takes the mother's serum, which contains her antibodies but no red blood cells, and mixes it with Rh+ red blood cells. Coombs reagent is then added. If agglutination occurs, the test is positive, and the mother must be producing anti-Rh antibodies. The direct Coombs test mixes the baby's red blood cells with Coombs reagent. If agglutination occurs, the test is positive, and the baby's red blood cells must have been attacked by its mother's anti-Rh antibodies.A woman who has never been pregnant has type B- blood. Which of the following antibodies would you expect to find in her serum?
To answer this question, you need to have an understanding of the ABO blood groups and what antigens its alleles code for. In addition, you need to have recalled from the passage that Rhimmunity requires prior sensitization, while ABO immunity does not, because of other naturally occurring antigens. Since the woman in the question has never been pregnant, it is highly unlikely that she has ever been exposed to the Rh antigen, which means that she would not pro- duce antibodies against it. So, choices C and D are wrong. Since her blood type is B, she would have anti-B antibodies, but would b expected to have anti-A antibodies because of a naturally occurring antigen that resembles the A antigen.
Four major blood types exist in the human ABO blood system: types A, B, AB, and O; and there are three alleles that code for them. The A and B alleles are codominant, and the O allele is recessive. Blood types are derived from the presence of specific polysaccharide antigens that lie on the outer surface of the red blood cell membrane. The A allele codes for the production of the A antigen; the B allele codes for the production of the B antigen; the O allele does not code for any antigen.While there are many other antigens found on red blood cell membranes, the second most important antigen is the Rh antigen. Rh is an autosomally dominant trait coded for by 2 alleles. If this antigen is present, an individual is Rh+; if it is absent, an individual is Rh-. For example, a person with type AB blood with the Rh antigen is said to be AB+.These antigens become most important when an individual comes into contact with foreign blood. Because of the presence of naturally occurring substances that closely mimic the A and B antigens, individuals who do not have these antigens on their red blood cells will form antibodies against them. This is inconsequential until situations such as blood transfusion, organ transplant, or pregnancy occur.Erythroblastosis fetalis is a condition in which the red blood cells of an Rh+ fetus are attached by antibodies produced by its Rh- mother. Unlike ABO incompatibility, in which there are naturally occurring antibodies to foreign antigens, the Rh system requires prior sensitization to the Rh antigen before antibodies are produced. This sensitization usually occurs during the delivery of an Rh+ baby. So while the first baby will not be harmed, any further Rh+ fetuses are at risk.The Coombs tests provide a method for determining whether a mother has mounted an immune response again her baby's blood. The tests are based on whether or not agglutination occurs when Coombs reagent is added to a sample. Coombs reagent contains antibodies against the anti-Rh antibodies produced by the mother. The indirect Coombs test takes the mother's serum, which contains her antibodies but no red blood cells, and mixes it with Rh+ red blood cells. Coombs reagent is then added. If agglutination occurs, the test is positive, and the mother must be producing anti-Rh antibodies. The direct Coombs test mixes the baby's red blood cells with Coombs reagent. If agglutination occurs, the test is positive, and the baby's red blood cells must have been attacked by its mother's anti-Rh antibodies.A medical student suggested giving Rh- mothers of Rh+ fetuses a specific exogenous substance prior to delivery to prevent an immune response. Which of the following substances would likely be the safest and most effective?
It is, in fact, true that a medical student was responsible for the treatment currently used to prevent Rh incompatibility reactions. The exogenous substance is called RhoGAM, and is derived from Rh immunoglobulin. RhoGAM is anti-Rh antibody. The theory behind it is that if given prior to delivery the time at which exposure occurs rhoGAM will attack and coat the fetal Rh positive red blood cells. By coating the fetal cells, the Rh antigen is no longer accessible to the mother's system; it is effectively "hidden." The mother therefore does not produce anti-Rh antibody of her own, the baby's coated red blood cells are removed and destroyed by the mother's immune system, and sensitization has been prevented. So choice C is correct. In practice, however, rhoGAM is usually administered during the postpartum period, specifically within the first 72 hours following birth. Choice A, Rh antigen, would only enhance the mother's immune response if given prior to delivery. Exposing her to the antigen would lead to the production of anti-Rh antibody, which would increase the risk of erythroblastosis fetalis for future children. The whole idea of the treatment is to prevent the mother from producing her own anti-Rh antibodies, and thereby prevent sensitization, NOT enhance it. So, choice A is wrong. Choice B, an immunosuppressive drug, might be an effective way to suppress the immune response, but it would certainly not be safe. An immunosuppressive drug has a broad action, rather than a specific one, and would affect many aspects of the mother's immune system, not just her ability to produce anti-Rh antibodies in response to the Rh antigen on her baby's red blood cells. In fact, immunosuppressive drugs would make the mother more susceptible to infection and would have adverse side effects. So choice B is also incorrect. Choice D, iron pills, are often given to pregnant women as an iron supplement to combat the anemia associated with pregnancy. The anemia is due to the excessive circulatory demands exacted by the fetus and the placentA. Iron pills, however, in no way affect the immune system and would therefore not be effective in preventing an immune response of any sort; thus choice D is incorrect.
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