Question 1

RhoGAM administered to an Rh-negative mother would help the patient by:
I- Preventing production of anti-Rh antibodies
II- Preventing fetal hemolysis in future pregnancies
III- Preventing transfusion reactions due to ABO mismatch

A) I only
B) III only
C) I and II
D) II and III
E) I, II, and III

I and II

Accepted Answer

RhoGAM prevents production of anti-Rh (anti-D) antibodies caused by an Rh incompatibility between an Rh-negative mother and an Rh-positive child during a pregnancy. By preventing production of anti-Rh antibodies, RhoGAM prevents fetal hemolysis in future pregnancies. However, RhoGAM would not prevent transfusion reactions from ABO mismatches because the D antigen is not part of the ABO antigen group.

Question 2

Which of the following is an example of an endogenous antigen?&#10;A) Viral protein&#10;B) Fungal cell wall&#10;C) Protein exotoxins&#10;D) Bacterial endotoxin

Accepted Answer

A viral protein is considered an endogenous antigen because the virus is inside of the host cell and the host cell is making the proteins for viral assembly. A fungal cell wall, endotoxins, and exotoxins enter the host from the outside environment and are presented on MHC class II molecules. A viral protein could also be considered exogenous because it comes from the outside, but in the context of this question, the viral protein is the only one that could be considered endogenous because it can be made by the host cell.

Question 3

Which of the following drugs can react with red blood cells (RBCs) to cause hemolysis?&#10;A) Penicillin&#10;B) Tetracycline&#10;C) Tolbutamide&#10;D) Procainamide

Accepted Answer

Procainamide is a hapten that readily binds to RBCs to create immunogenic neoantigens. Antibodies can react with the neoantigen to cause damage to the cell membrane, leading to hemolysis. Penicillin, tetracycline, and tolbutamide act as haptens and bind to carrier proteins, such as albumin, to act together as an immunogen, but they do not specifically react with RBCs to cause hemolysis.

Question 4

Isoantigens found on red blood cells (RBCs) may lead to a hemolytic transfusion reaction because: A) CD4⁺ T cells and macrophages mediate an inflammatory response B) Individuals have antibodies to the ABO antigens they do not express C) CD8⁺ T cells recognize the isoantigens as foreign and destroy the RBC D) The isoantigens are metabolized to reactive metabolites that cause an allergic reaction

Accepted Answer

Isoantigens (ABO antigens) on RBCs could be the cause of a hemolytic transfusion reaction if a patient were to be given blood of a different type. This can occur because individuals contain antibodies to the antigens that they do not possess. If a person was given donor blood of a type that possessed antigens that the patient did not have, then a rapid antibody-mediated hemolysis would occur. For example, if a patient has type A blood, then the patient has A antigens on the RBC surface, and anti-B antibodies circulating in the serum. If that patient were to be given type B or type AB RBCs, then the anti-B antibodies would hemolyze the donor cells. The patient could have received type A blood as a match, or type O blood because type O does not have A or B antigens on the cell surface, so no reaction would occur. This antibody-mediated reaction occurs through pre-existing antibodies, so T and B cell activation are not involved, and this is not an allergic response.

Question 5

Genetic factors that influence immunogenicity include:
I- Decreased functional capacity of the immune system over time
II- Lack of a T cell clone with a TCR that reacts to the antigen
III- Defect in antigen processing and antigen presentation

A) I only
B) III only
C) I and II
D) II and III
E) I, II, and III

Accepted Answer

Lack of a T cell clone with a reactive TCR and a defect in antigen processing and presentation are both potential genetic defects that could influence immunogenicity. Age-related decrease in functional capacity of the immune system affects immunogenicity, but is caused by age and not genetics.

Question 6

Production of a neoantigen would result from:&#10;A) Fungal infection&#10;B) Genetic mutation&#10;C) Presence of endotoxins&#10;D) Processing of parasitic antigens

Accepted Answer

A neoantigen is a new self antigen expressed on a cell and is the result of a genetic mutation. The genetic mutation could arise from a variety of circumstances, including viral infection or drugs, which could affect the genetic makeup of the cell. Fungal or parasitic infections and endotoxins are unlikely to cause genetic mutations.

Question 7

Which of the following represents a conformational epitope?&#10;A) A mannose residue&#10;B) Primary sequence of a short peptide&#10;C) Long chain carbon segment of a lipid&#10;D) Segment of two neighboring loops of a hemoglobin molecule

Accepted Answer

A conformational epitope occurs when a protein is folded into a tertiary structure, and a segment of two neighboring loops of a hemoglobin molecule would classify as conformational. The other options are primary sequences and would classify as linear epitopes.

Question 8

How would you treat a mother with type A Rh-negative blood who is pregnant with a type O Rh-positive baby?&#10;A) A dose of RhoGAM at 28 weeks and following delivery&#10;B) A high dose of RhoGAM and then a low dose of RhoGAM&#10;C) A dose of RhoGAM only if there is a trauma or premature termination of pregnancy&#10;D) RhoGAM is not necessary in this situation because there is no compatibility issue

Accepted Answer

RhoGAM is necessary in this situation because the mother is Rh-negative and the baby is Rh-positive, and if fetal blood enters the mother's body, then the mother will produce antibodies to the Rh antigen (D antigen). An Rh-negative mother should be treated with RhoGAM at 28 weeks to prevent production of Anti-Rh (anti-D) antibodies in the event that there is any exchange of blood between the mother and fetus. A second dose is given within 72 hours of delivery to allow the RhoGAM to coat any fetal red blood cells (RBCs) that may have crossed to the mother's blood stream during delivery. Coating the fetal RBCs prevents the mother's immune system from recognizing the cells as foreign, thus preventing antibody production to the Rh-antigen if the baby is Rh-positive. By preventing antibody production, future fetuses are not at risk for hemolytic anemia and erythroblastosis fetalis due to Rh incompatibility. Early in pregnancy, when the fetus is small, the dose is lower because the amount needed to neutralize the small amount of blood in the fetus is low. Later, when the fetus is larger, there is the possibility that more blood could be exchanged between mother and fetus, so the dose of RhoGAM required to neutralize the fetal cells in the mother is larger.

Question 9

When a low molecular weight (<3000 Da) pharmaceutical agent binds to albumin, the pharmaceutical agent is acting as a/an:&#10;A) Hapten&#10;B) Allergen&#10;C) Immunogen&#10;D) Carrier protein

Accepted Answer

The pharmaceutical agent is acting as a hapten because it is not immunogenic on its own, but when bound to albumin, which is a carrier protein, the two together become the immunogen. The two together could also be an allergen, but the pharmaceutical agent alone is not allergenic or immunogenic.

Question 10

Which of the following would be considered the best immunogen?&#10;A) Mannose&#10;B) Viral DNA&#10;C) Surface protein on a parasite&#10;D) Lipid components of fungal membrane

Accepted Answer

A surface protein meets the criteria for the best immunogen because it is foreign, large in size, degradable, and has a complex tertiary structure. Lipids, carbohydrates, and DNA are less effective immunogens because they do not have the rigid tertiary structure; in the case of mannose, it has a low molecular weight.

Deck 3: Immunogenicity and Antigenicity