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Immunology A Short Course, Fourth Edition
Eli Benjamini, Richard Coico, and Geoffrey Sunshine Paper • February 2000 • 500 pp. • 0-471-34890-2 |
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Primary interactions between antigens and antibodies involve all of the following
except
A)
covalent bonds.
B)
van der Waals forces.
C)
hydrophobic forces.
D)
electrostatic forces.
E)
a very close fit between an epitope and the antibody.
If an IgG antibody preparation specific for hen egg lysosome (HEL) is treated with
papain to generate Fab fragments, which of the following statements concerning the
avidity of such fragments is true?
A)
They will have a lower avidity for HEL as compared with the intact IgG.
B)
They will have a higher avidity for HEL as compared with the intact IgG.
C)
There will have the same avidity for HEL as the intact IgG.
D)
They will have lost their avidity to bind to HEL.
E)
They will have the same avidity but will have a lower affinity for HEL.
Western assays used to test serum samples for the presence of antibodies to infectious
agents, such as HIV, are particularly useful as diagnostic assays because
A)
they are more sensitive than ELISA.
B)
antibodies specific for multiple antigenic epitopes can be detected.
C)
they provide quantitative data for sample analysis.
D)
they allow multiple samples to be tested simultaneously.
E)
they are less expensive and take less time to perform as compared with ELISA.
The major difference between transgenic mice and knockout mice is that
A)
transgenic mice always employ the use of cloned genes derived from other species.
B)
transgenic mice have foreign genes that integrate at targeted loci through homologous
recombination.
C)
transgenic mice have a functional foreign gene added to their genome.
D)
knockout mice always have a unique phenotype.
SCID mice have a genetic defect that prevents development of functional
A)
hematopoietic cells.
B)
B cells and T cells.
C)
T cells and NK cells.
D)
pluripotential stem cells.
E)
myeloid cells.
Which of the following statements regarding B cell hybridomas is false?
A)
They are immortal cell lines that produce antibodies of a single specificity.
B)
They are derived from B cells that are first cloned and grown in cell culture for short
periods.
C)
They contain a large nucleus formed by the fusion of two nuclei.
D)
They can be used to manufacture diagnostic or therapeutic monoclonal antibodies.
E)
They are derived by fusing B cells with malignant plasma cells that are unable to secrete
immunoglobulin.
An ELISA designed to test for the presence of serum antibody for a new strain of
pathogenic bacteria is under development. Initially, a monoclonal antibody specific
for a single epitope of the organism was used both to sensitize the wells of the ELISA
plate and as the enzyme-labeled detecting antibody in a conventional sandwich
ELISA. The ELISA failed to detect the antigen despite the use of a wide range of
antibody concentrations. What is the most probable cause of this problem?
A)
The antigen is too large.
B)
The antibody has a low affinity for the antigen.
C)
The monoclonal antibody used to sensitize the wells is blocking access of the epitope, thus
when the same antibody is enzyme-labeled, it cannot bind to the antigen.
D)
The enzyme-labeled antibody used should have been a different isotype than the sensitizing
antibody.
E)
The monoclonal antibody used is probably unstable.
The indirect Coombs' test (anti-immunoglobulin test) typically uses:
A)
Patient's red cells to determine whether they will bind IgG
B)
patient's red cells to determine whether they will bind all immunoglobulins
C)
patient's serum to determine whether it forms a precipitate with donor plasma
D)
patient's serum to determine whether it contains antibodies that bind to a variety of reagent red cells
E)
patient's serum to determine whether it contains antibodies that bind to the patient's red cells
Answers To Review Questions
1. A No covalent bonds are involved in the interaction between antibody and antigen. The binding forces are relatively weak and include van der Waals forces, hydrophobic forces, and electrostatic forces. A very close fit between an epitope and the antibody is required.
2. A Avidity denotes the overall binding energy between antigens and multivalent antigens. Since the valency of the Fab fragments is one as compared with the HEL-specific IgG molecule, which has a valence of 2 (due to the presence of two Fab regions), the avidity of the fragments will be lower. Choice E is incorrect since the affinity of the Fab fragments will be the same as each of the Fab regions of the intact IgG molecule.
3. B In Western assays, electrophoretic separation techniques are used to resolve the molecular mass of a given antigen or mixtures of antigens. Since antibody responses to infectious agents generate polyclonal responses by virtue of the complex antigenic determinants expressed by such agents, Western assays can confirm the presence of these antibodies, which react with the electrophoretically separated antigens of known molecular weights.
4. C Cloned foreign genes from either the same or other species are introduced into mice to generate a transgenic strain. Integration is random and occurs in both somatic and germ line cells. Choice D is incorrect because sometimes knockout mice do not have a phenotype unique caused by the replacement of a functional gene with one that is nonfunctional, probably due to the activity of redundant or compensatory mechanisms.
5. B SCID mice possess an autosomal recessive mutation that causes a disorder in which B and T cells fail to develop. Like their human counterparts, SCID mice are compromised with respect to lymphoid defense mechanisms. Pluripotential stem cells present in SCID mice can give rise to other hematopoietic lineages, including cells in the myeloid lineage and NK cells.
6. B The method used to generate B cell hybridomas employs the fusion of B cells (e.g., from the spleen and lymph nodes) harvested from immunized mice with a selected population of malignant plasma cells unable to secrete immunoglobulin. Antigen-specific B cells are not cloned first and then fused with such plasma cells.
7. C In a sandwich ELISA, an antibody (often monoclonal) is used to coat ELISA wells followed by blocking with a nonspecific protein to saturate any unbound sites. The antigen is then added, followed by the addition of a second antigen-specific antibody that is enzyme- labeled. A polyclonal, antigen-specific antibody is often used as the enzyme-labeled reagent. This is done because the epitope detected by the coating antibody (a monoclonal antibody in this case) may be blocked by that antibody, thus preventing its access if the same monoclonal were used as the enzyme-labeled detecting antibody.
8. D The indirect Coombs test is generally used to detect the presence in a patient's serum of antibodies that react with antigens expressed on red blood cells (see Figure 5.2).
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