IMMUNOLOGY AND SEROLOGY

Question 1

Natural barriers of the immune system include all except which of the following?
a. pH of secretions
b. Coughing
c. Hair follicles
d. Intestinal bacteria

Answer 1

c. Hair follicles

Low acidic environment and enzymes in secretions, coughing, and gastrointestinal tract and skin bacteria are natural barriers to invading pathogens and antigens.

Question 2

The fundamental difference between primary and secondary organs of the lymphatic system is:
a. Antibody production occurs only in the primary lymph organs
b. Complement production occurs only in the primary lymph organs
c. Maturation of lymphocytes occurs in secondary organs, and activation occurs in primary organs
d. Maturation of lymphocytes occurs in primary organs, and activation occurs in secondary organs

Answer 2

d. Maturation of lymphocytes occurs in primary organs, and activation occurs in secondary organs

The primary organs are where lymphocytes reside to mature. Once mature, they leave the primary organs and migrate to the secondary organs, where they await activation.

Question 3

Toll-like receptors act in which way?
a. Enhance recognition of bacteria by phagocytic cells
b. Activate B cells to produce antibody
c. Activate helper T cells
d. Aid in processing antigen in the form of an MHC molecule

Answer 3

a. Enhance recognition of bacteria by phagocytic cells

Toll-like receptors (TLRs) are molecules on phagocytic cells that recognize certain substances or molecules that reside on surfaces of some bacteria. The TLRs recognize and bind to these substances, enhancing the phagocytic process.

Question 4

Neutrophils and monocytes have receptors for which part of the immunoglobulin molecule?
a. Fc
b. Fab
c. Hinge region
d. Variable region

Answer 4

a. Fc

Once bound to a specific antigen, antibodies can act as opsonins. The Fc portion of the immunoglobulin molecule attaches to the receptor molecules on monocytes and neutrophils to enhance phagocytosis.

Question 5

One B-cell marker of early stage B-cell development is _____, whereas ____ is a marker for later stages of B-cell development.
a. CD20; CD10
b. CD21; CD10
c. CD10; CD20
d. CD19; CD10

Answer 5

c. CD10; CD20

CD10 appears early in the B-cell development and is lost after the immature stage, making this an early B-cell marker. CD20 begins to appear during the immature stage of B-cell development; it is found on the later stages and is a marker for the later stages of B-cell development.

Question 6

A double-positive T cell would express which markers?
a. CD4 +CD8 +CD3+
b. CD4- CD8 + CD3+
c. CD4- CD8- CD3-
d. CD4 +CD8- CD3+

Answer 6

a. CD4 +CD8 +CD3+

At the double-positive stage of development, this T cell expresses both CD4 and CD8.

Question 7

Which cell is considered to be a bridge between the innate and adaptive immune systems?
a. NK cell
b. Mast cell
c. Monocyte-macrophage
d. T cell

Answer 7

a. NK cell

Natural killer (NK) cells are lymphocytes (cells of the adaptive immune system) that have a cytotoxic effect against cellular pathogens without prior known exposure (innate system characteristic). Thus these cells have been considered a bridge between the systems.

Question 8

_______ are involved in cell mediated immunity, whereas _______ are involved in humoral immunity.
a. T cells; B cells
b. T cells; antibodies
c. B cells; T cells
d. A and B

Answer 8

d. A and B

T cells are involved in cell-mediated immunity, whereas B cells that make antibodies are involved in humoral immunity.

Question 9

Antigens that make very good immunogens include which of the following?
a. Carbohydrates
b. Proteins
c. Both a and b
d. Neither a or b

Answer 9

b. Proteins

Proteins that are made up of amino acids can be much more structurally and conformationally complex than the sugars of carbohydrates.

Question 10

The function of the complement system include(s) which of the following?
a. Clearance of cellular debris
b. Chemotaxis
c. Lysis of bacteria
d. All of the above

Answer 10

d. All of the above

The complement pathways result in cell lysis. Other complement proteins released after complement activation can have chemotactic properties. Complement proteins also act as opsonins to enhance phagocytosis to help clear debris from inactive and dead cells.

Question 11

When C3 is cleaved by C3 convertase, what is the result?
a. C3a is released
b. C3b is used as an opsonin
c. C3b is combined with other complement proteins to form C5 convertase
d. All of the above

Answer 11

d. All of the above

C3 convertase cleaves C3 to C3a and C3b. C3a is released into the plasma and can act as an anaphylatoxin. C3b is released to combine with C42a in the classical pathway or C3bBb in the alternate pathway of complement activation to form C5 convertase. Extra C3b proteins can act as an opsonin by coating pathogens and attachment to the Fc portion of immunoglobulins.

Question 12

Characteristics of cytokines include which of the following?
a. They can have a pleomorphic effect
b. Cytokines are redundant
c. Cytokines enhance cellular differentiation of lymphocytes
d. All of the above

Answer 12

d. All of the above

Certain cytokines produced can enhance the differentiation of lymphocytes to maturity. Cytokines can have many different effects (pleomorphic) on cells outside of the immune system. Also, different cytokines can have the same effect on the same cell, thus making them redundant.

Question 13

Immunoglobulin idiotypes are antibodies with variations in the domains of which of the following?
a. CH1 and CH2
b. VH and VL
c. VH and CL
d. CH1, CH2, and CH3

Answer 13

b. VH and VL

Variations in the variable regions of the heavy and light chains of an immunoglobulin molecule define the idiotype.

Question 14

Mannose-binding lectin is similar to which component of the classical pathway?
a. C3
b. C2
c. C1q
d. C5a

Answer 14

c. C1q

Mannose-binding lectin (MBL) of the lectin pathway of complement activation is found in circulation complexed with proteinases. It is considered to be similar in structure to C1q of the classical pathway. The MBL proteinase complex does not require antibody for complement activation.

Question 15

A patient with a viral infection to the ABC virus is found to have a high antibody titer to the ABC virus’s RNA, or anti-ABCr. Which of the following is true?
a. MHC class I molecules presented antigen to CD4+ T cells
b. MHC class II molecules presented antigen to CD8+ T cells
c. MHC class I molecules presented antigen to CD8+ T cells
d. MHC class II molecules presented antigen to CD4+ T cells

Answer 15

c. MHC class I molecules presented antigen to CD8+ T cells

Viruses use cellular mechanisms and processes for replication. These antigens synthesized inside a cell are expressed on the cell surface in the form of major histocompatibility complex (MCH) class I molecules, which are then presented to CD8 cytotoxic T lymphocytes for cell lysis.

Question 16

What is the main difference between agglutination and precipitation reactions?
a. Agglutination occurs between a soluble antigen and antibody
b. Agglutination occurs when the antigen is particulate
c. Precipitation occurs when the antigen is particulate
d. Precipitation occurs when both antigen and antibody are particulate

Answer 16

b. Agglutination occurs when the antigen is particulate

Precipitation reactions occur between soluble antigen and soluble antibody that produce a visible end result typically in the form of a visible line of precipitate. Agglutination reactions occur when the antigen is particulate or coated on a particulate such as latex beads.

Question 17

Postzone causes false negative reactions in antibody titers as a result of which of the following?
a. Too much diluent added to test
b. Excess antibody in test
c. Excess antigen in test
d. Incorrect diluent added to test

Answer 17

c. Excess antigen in test

In agglutination tests where postzone is occurring, there are so many antigens in the test system, that each antibody reacts singly with the antigen, so no lattice formation occurs and false negative reactions are seen.

Question 18

Antibodies produced against two or more epitopes of specific antigen are considered ____________.
a. Monoclonal
b. Pleomorphic
c. Dimorphic
d. Polyclonal

Answer 18

d. Polyclonal

Antibodies that react against different antigenic determinants (epitopes) of the same specific antigen are considered to be polyclonal.

Question 19

In the radial immunodiffusion test, the gel contains which of the following?
a. The antigen to be tested
b. Antibody
c. Patient sample
d. None of the above; the gel is the medium to which the
antibody and antigen are applied in equal proportion

Answer 19

b. Antibody

In radial immunodiffusion, known antibody is added to the gel. Patient serum contains the antigen to be tested

Question 20

Which statement is true regarding the radial immunodiffusion test?
a. The area of the precipitin ring is directly proportional to the concentration of antigen in the sample
b. The area of the precipitin ring is directly proportional to the concentration of antibody in the sample
c. The area of the precipitin ring is directly proportional to the concentration antibody and the antigen in the sample
d. The area of the precipitin ring indicates a partial identity to the antibody in the sample

Answer 20

a. The area of the precipitin ring is directly proportional to the concentration of antigen in the sample

The patient serum contains the antigen to be
tested. The gel contains known specific antibody. The area of the precipitation ring around the center well is directly proportional to the concentration of the antigen in the sample tested.

Question 21

The indirect antiglobulin test is for ______________, whereas the direct antiglobulin test is for__________.
a. Serum antigen; bound antigen
b. Serum antigen; bound antibody
c. Serum antibody; bound antigen
d. Serum antibody; bound antibody

Answer 21

d. Serum antibody; bound antibody

The indirect antiglobulin uses commercial red cells with known antigens to test for unknown antibody in a patient serum sample (e.g., antibody screening test). The direct antiglobulin tests patient red cells coated with antibody that occurred in vivo (e.g., hemolytic disease of the newborn).

Question 22

In an indirect immunofluorescent antibody test for CMV antibodies, the conjugated antibody used for visualizing is:
a. Antihuman globulin conjugated to a fluorescent dye
b. Anti-CMV antibody conjugated to a fluorescent dye
c. CMV virus conjugated to a fluorescent dye
d. Antihuman globulin conjugated to an enzyme

Answer 22

a. Antihuman globulin conjugated to a fluorescent dye

Indirect tests are performed in two steps. The first step is incubating (cytomegalovirus [CMV]) antigen with specific antibody (patient serum). The second step is adding anti human globulin (antibody to CMV antibody) coupled with the fluorescent dye for visualizing the reaction.

Question 23

What is the difference between nephelometry and turbidimetry?
a. There is no difference between the two assays, only in name
b. Nephelometry is a newer example of turbidimetry
c. Nephelometry measures light transmitted through a solution, and turbidimetry measures light scattered in a solution
d. Nephelometry measures light scattered in a solution, and turbidimetry measures light transmitted through a solution

Answer 23

d. Nephelometry measures light scattered in a solution, and turbidimetry measures light transmitted through a solution

Nephelometry measures light at angles. The light source used for detection is placed at an angle from the detection device. Turbidometry detection devices are placed directly across from the light source and measures the intensity of the light as it passes through solution.

Question 24

In an Ouchterlony immunodiffusion, the line of precipitation between the
antibody and the antigen wells forms an X. This reaction would be described as which of the following?
a. Nonidentity
b. Partial identity
c. Identity

Answer 24

a. Nonidentity

A crossed line in the Ouchterlony diffusion indicates the antigens do not share epitopes in common and is therefore considered nonidentity.

Question 25

An initial titer of 4 followed by a subsequent titer of 16 for the same patient, drawn 2 weeks later, is indicative of which of the following?
a. Infection
b. Convalescence
c. Past exposure
d. No exposure

Answer 25

a. Infection

In a twofold serial dilution, a rise in titer results between the initial titer and subsequent titer of more than two tubes or fourfold, the results are considered diagnostic of infection.

Question 26

A deficiency of T cells can result in which of the following?
a. Low levels of complement
b. Dysfunctional macrophages
c. Fewer B cells maturing to plasma cells
d. Contact dermatitis

Answer 26

c. Fewer B cells maturing to plasma cells

On activation, certain subsets of T lymphocytes produce growth-enhancing cytokines that act on B cells to mature to antibody-secreting plasma cells. B cells would not be able to mature if a deficiency of T cells existed.

Question 27

A 2-week-old baby is seen for a possible infection with CMV. Which of the following statements is false?
a. A positive anti-CMV result from baby’s specimen is inconclusive
b. An initial titer of anti-CMV IgG would need to be established
c. A positive result for anti CMV IgM would indicate infection
d. All are false statements

Answer 27

b. An initial titer of anti-CMV IgG would need to be established

In the serum of a 2-week-old baby, a titer of IgG anticytomegalovirus would be representative of the maternal antibody that crossed the placenta and not the baby’s antibody.

Question 28

What is the basic difference between the RPR and VDRL tests?
a. The RPR detects antigen, whereas the VDRL detects antibody
b. The RPR test is read macroscopically, whereas the VDRL is read microscopically
c. The RPR test is a treponemal test, whereas the VDRL is nontreponemal
d. There is no difference because they are both specific tests for syphilis

Answer 28

b. The RPR test is read macroscopically, whereas the VDRL is read microscopically

Both rapid plasma reagin (RPR) and Venereal Disease Research Laboratory (VDRL) tests are nontreponemal tests that detect antibody to cardiolipin. The RPR test is a macroscopic agglutination, and the VDRL test is read microscopically

Question 29

A patient has the following hepatitis B serology:
HBsAg: Negative
Anti-HBc: Positive
Anti-HBS: Positive

These results are consistent with which of the following?
a. Acute hepatitis B
b. Chronic hepatitis B
c. Recovery from hepatitis B
d. Acute hepatitis A

Answer 29

c. Recovery from hepatitis B

The presence of anti-HBs in patient serum is indicative of recovery from a hepatitis B infection. It also may indicate immunity resulting from vaccination.

Question 30

The HLA genes are inherited as:
a. Diplotypes: Two diplotypes from each parent
b. Haplotypes: One haplotype from each parent
c. HLAs are not inherited, instead are proteins absorbed onto cells
d. Only the HLA-A antigen is an inheritable trait

Answer 30

b. Haplotypes: One haplotype from each parent

Human leukocyte antigen (HLA) genes are inherited as haplotypes; one haplotype from each parent.

Question 31

Agglutination and precipitation that is visible depends on antigen–antibody ratios ________.
a. With antigen in excess
b. With antibody in excess
c. That are equivalent
d. All of the above

Answer 31

c. That are equivalent

Visible agglutination and precipitation reactions depend on the antigen and antibody concentrations that are in equivalence. It is at this point that precipitation and lattice formation occurs. Too much antigen results in postzone phenomenon, and too much antibody results in prozone.

Question 32

Which of the following cell types is implicated in immediate hypersensitivity?
a. Neutrophil
b. Mast cell
c. Macrophage
d. Monocyte

Answer 32

b. Mast cell

Type I hypersensitivity occurs as a result of the release of the granular contents of mast cells when bound to IgE antibodies cross linked with antigen.

Question 33

Anti-dsDNA antibodies are associated with which of the following?
a. Syphilis
b. CMV infection
c. Systemic lupus erythematosus
d. Hemolytic anemia

Answer 33

c. Systemic lupus erythematosus

Anti-dsDNA autoantibodies are present in patients with systemic lupus erythomatosus and, when identified, can be considered diagnostic of the disease.

Question 34

Rheumatoid factor is typically an IgM autoantibody with specificity for which of the following?
a. SS-B
b. Double-stranded DNA
c. Ribonucleoprotein
d. Fc portion of IgG

Answer 34

d. Fc portion of IgG

The rheumatoid factor is antibody directed
against the Fc portion of the IgG molecule.

Question 35

All of the following are autoimmune diseases except:
a. Rheumatoid arthritis
b. Rh disease of the fetus and newborn
c. Grave’s disease
d. Myasthenia gravis

Answer 35

b. Rh disease of the fetus and newborn

Rh disease of the fetus and newborn is not an autoimmune disease but is classified as a type II hypersensitivity reaction.

Question 36

In Grave’s disease, one of the main autoantibodies is:
a. Anti-CCP
b. Antibody to islet cells of pancreas
c. Antibody to thyroid-stimulating hormone receptor
d. Anti-dsDNA

Answer 36

c. Antibody to thyroid-stimulating hormone receptor

Autoantibody to the thyroid-stimulating hormone receptor ultimately causes release of thyroid hormones and a hyperthyroid condition.

Question 37

An autoantibody found in patients with Hashimoto’s thyroiditis reacts with which of the following?
a. TSH receptor
b. Islet cells
c. CRP
d. Thyroglobulin

Answer 37

d. Thyroglobulin

Antithyroglobulin is a common autoantibody in Hashimoto’s thyroiditis resulting in elevated levels of thyroid-stimulating hormone and hypothyroidism.

Question 38

Skin testing for exposure to tuberculosis is an example of which type of hypersensitivity?
a. Type I
b. Type II
c. Type III
d. Type IV

Answer 38

d. Type IV

Type IV hypersensitivity is the delayed-type hypersensitivity. Skin testing for tuberculosis causes a delayed-type hypersensitivity to intradermally injected antigens in individuals previously exposed to the organism.

Question 39

Which of the following is a test for specific treponemal antibody?
a. VDRL
b. RPR
c. FTA-ABS
d. All of the above

Answer 39

c. FTA-ABS

The fluorescent treponemal antibody absorption (FTA-ABS) test is a confirmatory test that detects specific antibodies to Treponemal pallidum in patient specimen.

Question 40

Serum tested positive for HBsAg and anti-HBc IgM. The patient most likely has which of the following?
a. Acute hepatitis C
b. Chronic hepatitis B
c. Acute hepatitis B
d. Acute hepatitis A

Answer 40

c. Acute hepatitis B

The most likely answer is acute hepatitis B because of the presence of IgM anti-HBc in combination with the hepatitis surface antigen. Typically the presence of IgM indicates the presence of an acute phase of a disease.

Question 41

The main difference between leukemias and lymphomas is which of the following?
a. Leukemias are malignancies of cells in the bone marrow
b. Lymphomas are malignancies of cells in the bone marrow
c. Lymphomas are classified as either acute or
chronic
d. Leukemias are malignancies in lymphoid tissue

Answer 41

a. Leukemias are malignancies of cells in the bone marrow

Lymphomas are generally classified as malignancies of lymphoid tissue. Leukemias are generally classified as malignancies of hematopoietic cells of the bone marrow or peripheral blood. Both can be classified as acute or chronic.

Question 42

A 1-year-old boy is seen for having many recurrent infections with Streptococcus pneumoniae. Laboratory tests revealed a normal quantity of T cells, but no B cells and no immunoglobulins were seen on electrophoresis. Which of the following would most likely be the cause?
a. Chronic granulotomatous disease
b. Bruton’s agammaglobulinemia
c. DiGeorge’s syndrome
d. Wiskott-Aldrich syndrome

Answer 42

b. Bruton’s agammaglobulinemia

Bruton’s agammaglobulinemia is typically seen in infancy. These patients present with frequent recurring infections, especially after protective maternal antibody is gone and normal levels of circulating T cells. The syndrome is a genetic B cell enzyme deficiency in which the B cells fail to differentiate and mature to antibody-producing plasma cells.

Question 43

A patient with hereditary angiodema has which of the following deficiencies?
a. C5-9
b. Phagocytic cell function
c. Mature B cells
d. C1 Inhibitor

Answer 43

d. C1 Inhibitor

Hereditary angioedema is characterized by recurrent swelling. The condition is genetic or can be acquired and is the result of a deficiency of the complement protein C1 Inhibitor.

Question 44

A radiograph of a 1-year-old boy indicates the lack of a thymus. Complete blood count and flow cytometry confirm a below-normal lymphocyte count and a lack of T cells. Which of the following would most likely be the cause?
a. DiGeorge’s syndrome
b. Wiskott-Aldrich syndrome
c. Bare lymphocyte syndrome
d. Bruton’s agammaglobulinemia

Answer 44

a. DiGeorge’s syndrome

DiGeorge syndrome is the most likely cause. In this syndrome the thymus fails to develop before birth. These patients also show a marked decrease in T cells.

Question 45

Severe combined immunodeficiency is characterized by which of the following?
a. Diagnosed in infancy
b. Shortened life span
c. No antibody production
d. All of the above

Answer 45

d. All of the above

Severe combined immunodeficiency is a genetic condition diagnosed in infancy. Both B-cell and T-cell development/function are arrested, resulting in no cell-mediated or humoral immunity.

Question 46

A 3-year-old boy is seen by his physician because of many recent bacterial infections. Flow cytometry indicates normal levels of T and B cells. The nitroblue tetrazolium test for oxidative reduction is negative. The most likely cause is:
a. Wegener’s syndrome
b. Chronic granulomatous disease
c. Bruton’s agammaglobulinemia
d. Diabetes mellitus

Answer 46

b. Chronic granulomatous disease

Chronic granulomatous disease is an inherited disease that impairs the neutrophil’s ability to kill certain bacteria. The neutrophils lack the enzyme nicotinamide adenine dinucleotide phosphate oxidase, easily demonstrated by the failure to reduce nitroblue tetrazolium or produce a blue end result. These patients have normal levels of lymphocytes.

Question 47

A 25-year-old man was seen by his physician for recurrent infections. Immunoelectrophoresis revealed hypogammaglobulinemia. This man most likely has which of the following?
a. Bruton’s agammaglobulinemia
b. Common variable immunodeficiency
c. X-linked agammaglobulinemia
d. DiGeorge’s syndrome

Answer 47

b. Common variable immunodeficiency

Because common variable immunodeficiency is commonly diagnosed in early adulthood, this is the most likely explanation for this case study. Bruton’s, X linked agammaglobulinemia, and DiGeorge’s syndrome are all typically identified in infancy.

Question 48

In which disease would you expect to see an IgM spike on electrophoresis?
a. Transient hypogammaglobulinemia of infancy
b. Wiskott-Aldrich syndrome
c. Leukocyte adhesion disease
d. Waldenstrom’s macroglobulinemia

Answer 48

d. Waldenstrom’s macroglobulinemia

Waldenstrom’s macroglobulinemia is a disease resulting from an overproduction of an IgM producing B-cell population. The monoclonal IgM can be seen as a spike on electrophoresis.

Question 49

A person has an infected bug bite with pain, swelling, and redness. What is the cause of these physical symptoms of inflammation?
a. Production of antibody
b. Secondary immune response
c. Increased blood flow and neutrophils to site
d. Activation of NK cells

Answer 49

c. Increased blood flow and neutrophils to site

Inflammation is caused by the increased blood flow and subsequent influx of neutrophils and other cells to an infected site. The increased blood flow and activity of the cells, including cytokine production, results in the redness, pain, and swelling to the area.

Question 50

The type of graft rejection that occurs within minutes of a tissue transplant is ____________.
a. Acute
b. Chronic
c. Hyperacute
d. Accelerated

Answer 50

c. Hyperacute

The hyperacute tissue graft reject occurs within minutes to hours of a transplant and is typically associated with transplantation across ABO blood groups and anti-ABO antibodies.