Question 1

At what age do infants begin to produce their own antibodies?

Accepted Answer

Infants begin to produce their own antibodies around 6 months of age. Before this, they rely on maternal antibodies passed through the placenta and breast milk.

Question 2

Which of the following blood group systems is not likely to cause HDN?

Accepted Answer

The MN blood group system is not likely to cause Hemolytic Disease of the Newborn (HDN) because the antibodies produced against this system are usually of IgM class which cannot cross the placenta. In contrast, the antibodies produced against the other systems (Kell, ABO, and Rh) are usually of IgG class which can readily cross the placenta and cause HDN.

Question 3

What test is used to remove autoantibodies from test serum?

Accepted Answer

Adsorption is the process of selectively removing autoantibodies from test serum by exposing the serum to a solid phase antigen that will bind the autoantibodies, allowing the non-specific and non-reactive antibodies in the serum to be used in subsequent testing. Direct and Indirect Coombs' tests are used to detect antibodies on red blood cells, and Elution is the process of removing antibodies from red blood cells for further testing.

Question 4

Which IgG subclass primarily comprises antibodies to the Rh blood group system?

Accepted Answer

The answer of Which IgG subclass primarily comprises antibodies to...

Question 5

What is responsible for recognition of the antibody-binding site to homologous antigen?

Accepted Answer

The variable region of the light and heavy chain of an antibody is responsible for binding to the homologous antigen. This region contains complementarity-determining regions (CDRs) that form the antigen-binding site through complementary interactions with the antigen. Phenotype and solubility of the antigen do not directly affect recognition by the antibody.

Question 6

What is the definition of an immunoglobulin?

Accepted Answer

An immunoglobulin, also known as an antibody, is a protein molecule produced in response to an antigen. It specifically recognizes and binds to antigens, helping to neutralize or eliminate them from the body.

Question 7

An agglutination inhibition test is performed on a person whose blood type is A+. The person's saliva is mixed with type A antisera. After incubation, the solution is mixed with reagent A cells and no agglutination occurs. What can be deduced from this finding?

Accepted Answer

If no agglutination occurs in the agglutination inhibition test with type A antisera, it indicates that the person has A antigen in their saliva, which has inhibited the agglutination of reagent A cells with type A antisera. This means the person is a secretor of A substance. Therefore, option C is the correct answer.

Question 8

Extravascular hemolysis occurs when red blood cells are coated with antibody; what organ sequesters these cells?

Accepted Answer

Extravascular hemolysis occurs when red blood cells are coated with antibody, causing them to be removed from circulation by the immune system. The organ that primarily sequesters these cells is the reticuloendothelial system, which includes the spleen, liver, and lymph nodes. The thymus and bone marrow are involved in other aspects of immune function, but are not directly responsible for removing red blood cells in extravascular hemolysis.

Question 9

Which of the following statements is true concerning immunoglobulin variations?

Accepted Answer

Isotypic variation refers to differences in immunoglobulin molecules between members of the same species, while allotypic variations occur between individuals within a species and can occur in both the constant and variable regions. Idiotypic variation refers to differences in the antigenic determinants found in the variable region of immunoglobulin molecules. Isotypic variation is not necessarily associated with organ transplantation or paternity testing, as those procedures typically focus on differences between individuals rather than the variability inherent in all members of a species.

Question 10

Which immunoglobulin exists in a pentameric configuration?

Accepted Answer

IgM exists in a pentameric configuration, meaning that it is composed of five subunits joined together. This allows IgM to be highly effective at agglutinating antigens and activating complement, making it important in the early stages of an immune response.

Question 11

Name a lymphoid organ in which cells of the immune system can be found.

Accepted Answer

Cells of the immune system can be found in all three of these lymphoid organs. The thymus is important for the development and maturation of T cells, bone marrow produces and supports hematopoietic stem cells that can differentiate into various immune cells, and the spleen filters blood and contains immune cells such as lymphocytes and macrophages.

Question 12

Only 5% of Kell-negative individuals will develop antibodies to Kell if exposed to the Kell antigen, whereas 50% to 70% of Rh(D)-negative individuals would produce antibodies to D upon exposure. What is the reason for this?

Accepted Answer

The difference in the immunogenicity of the Kell antigen compared to the D antigen leads to the lower percentage of Kell-negative individuals developing antibodies upon exposure. ABO type and phenotype are not significant factors in this case.

Question 13

At what temperature do IgM antibodies react?

Accepted Answer

IgM antibodies typically react at lower temperatures, around 22°C, which is considered the optimal temperature for their activity in cold agglutinin disease.

Question 14

IgG-coated RBCs will be phagocytized by what effector cells?

Accepted Answer

Monocytes/macrophages are the primary effector cells for phagocytosis of IgG-coated RBCs. These cells express Fcγ receptors, which bind the Fc portion of the IgG antibodies coating the RBCs, triggering phagocytosis. T cells, eosinophils, and basophils do not have the same capacity for phagocytosis as monocytes/macrophages, and are not typically involved in the clearance of antibody-coated cells.

Question 15

What class of immunoglobulin is capable of crossing the placenta?

Accepted Answer

Immunoglobulin G (IgG) is the only class of immunoglobulin that is capable of crossing the placenta from the mother to the fetus. This provides passive immunity to the newborn during the first few months of life until their own immune system develops. IgM, IgE, and IgD do not cross the placenta.

Question 16

Which of the following is not true of monoclonal reagents?

Accepted Answer

Monoclonal reagents are produced for single antigens with only one epitope, not more than one epitope.

Question 17

What is a possible explanation for a weak reaction (1+) in a reverse ABO grouping test?

Accepted Answer

All of the above could contribute to a weak reaction in a reverse ABO grouping test. An elderly patient may have a weaker immune response, an immunocompromised patient may have decreased antibody production, and an IgM deficiency could result in a weaker detection of anti-A or anti-B antibodies.

Question 18

How can T cells be differentiated from B cells?

Accepted Answer

T cells can be differentiated from B cells by several methods, including the secretion of interleukin-2, the presence of the CD2 marker, and the ability to agglutinate sheep erythrocytes. All these characteristics are associated with T cells, distinguishing them from B cells.

Question 19

A person with the genotype MM shows a 3+ reaction when red blood cells are mixed with M antisera; whereas a person with the genotype MN shows a 1+ reaction. What phenomenon is occurring here?

Accepted Answer

This is an example of dosage effect, where the homozygous individual with two copies of the M allele shows a stronger reaction than the heterozygous individual with only one copy of the M allele. Prozone occurs when there is an excess of antibodies that can interfere with the agglutination reaction, but this is not the case here. Zeta potential refers to the electrical charge around cells or particles that can affect their interactions, but it is not relevant in this scenario. Hemolysis refers to the breaking down of red blood cells, which is not happening here either.

Question 20

What is the purpose of the antihuman globulin (AHG) test in blood banking?

Accepted Answer

The antihuman globulin (AHG) test, also known as the Coombs test, is a blood test used in blood banking to detect the presence of antibodies that have coated red blood cells. These antibodies may be naturally occurring, as in hemolytic disease of the newborn, or may have been transfused into the patient. The AHG test works by bridging the gap between red blood cells that have been coated with antibody, causing them to agglutinate, or clump together. This clumping can then be detected, allowing for identification of incompatible blood transfusions or other blood-related disorders. The AHG test does not detect white blood cells coated with antibody or red blood cells coated with antigen.

Quiz 3: Fundamentals of Immunology