EVALUATIVE EXAM (SEROLOGY) Flashcards
Color Plate 21B depicts a monomeric
immunoglobulin molecule. The portion of
the molecule indicated by the dotted red
circle and the red arrow is called the
A. Fab fragment
B. Fc fragment
C. Heavy chain
D. Hinge region
A. The basic structure of all immunoglobulins
is two light chains joined to two heavy chains
by disulfide bonds. The amino terminus of both
the heavy and light chains, together, constitutes
the Fab fragment (fragment of antigen binding).
The carboxy-terminus of the heavy chains constitutes the Fc fragment. The hinge region is the
area at the center of the “Y,” near the carboxyterminus of the light chains.
A hapten is
A. Half of an immunoglobulin molecule
B. A earner molecule for an antigen that
is not antigenic alone
C. An immunoglobulin functional only in
the presence of complement
D. A determinant capable of stimulating
an immune response only when bound
to a carrier
D. Haptens are substances that are not immunogenic by themselves. These molecules are not
large or complex enough to stimulate the immune
system. When bound to a carrier, they are capable
of stimulating a specific immune response
Which of the following is characteristic of
B cells?
A. Phagocytic
B. Participate in antibody-dependent
cellular cytotoxicity (ADCC) reactions
C. Contain surface immunoglobulins
D. Secrete the C5 component of
complement
C. B cells carry surface immunoglobulins that
react to a specific antigen. The antigen can then be
internalized processed and presented to an appropriate T helper cell. B cells are not phagocytic,
nor do they participate in antibody-dependant cellular cytotoxicity (ADCC) reactions. Complement proteins are secreted by hepatocytes.
A lymphokine is
A. A soluble mediator produced by
granulocytes and affecting lymphocytes
B. A soluble mediator produced by
lymphocytes
C. A soluble mediator produced by
plasma cells
D. An antibody that reacts with
lymphocytes
B. Lymphokines are soluble mediators of
immune reactions. They are produced most often
by T lymphocytes. Antibodies are produced by plasma cells.
Monocytes and macrophages play a major
role in the mononuclear phagocytic
system. For an antibody-coated antigen to
be phagocytized, what part of the antibody
molecule fits into a receptor on the
phagocytic cell?
A. Fc region
B. Fab region
C. Hinge region
D. Variable region
A. The Fc region of an IgG molecule fits into an
Fc receptor (FcR) on macrophages and monocytes. The Fc receptor binds to specific amino acid residues in the Fc region of the immunoglobulin. The variable region of immunoglobulin
binds to the antigen
Cell-mediated immunity is primarily
mediated by
A. B cells
B. T helper cells
C. Plasma cells
D. Dendritic cells
B. T helper cells are the primary mediators of
cell-mediated immunity (CMI). They secrete
several different lymphokines that stimulate a
number of other cells, such as cytotoxic T lymphocytes and monocytes. B cells differentiate
into plasma cells during a humoral-mediated
immune response. Dendritic cells are important
antigen presenting cells, but they are not the primary mediators of a CMI response.
The HLA complex is located primarily on
A. Chromosomes
B. Chromosome 6
C. Chromosome 9
D. Chromosome 17
B. The HLA system is part of a larger region
known as the major histocompatibility complex.
It is located on chromosome 6. The region is
located on the short arm of the chromosome.
Chromosome 15 contains one HLA gene, B2M
HLA antigens are found on
A. All nucleated cells
B. Red blood cells only
C. Solid tissue only
D. White blood cells only
A. Human leukocyte antigens (HLAs) are a
group of antigens originally described on human
white cells. It is now known that they are found
on all nucleated cells of the body, including solid
tissue cells. HLAs are not found on red blood
cells.
Which of the following is more likely to
be diagnostic of an acute infection?
A. A total acute antibody titer of 2
followed by a convalescent titer of 16
B. A total acute antibody titer of 80
followed by a convalescent titer of 40
C. A total antibody titer of 80
D. An IgG antibody titer of 80
A. The most significant indicator of acute or
recent infection is the presence of a rising antibody liter. A fourfold or greater rise in titer, from
2 to 16, is significant. Even relatively high antibody liters of IgG may indicate past infection.
IgM is produced first following infections, so a
high IgM titer is also suggestive of an acute
infection
A young woman shows increased
susceptibility to pyogenic infections.
Upon assay, she shows a low level of C3.
Which of the following statements is
probably true?
A. She has an autoimmune disease with
continual antigen-antibody activity
causing consumption of C3.
B. She has DiGeorge syndrome.
C. She has decreased production of C3.
D. She may produce an inactive form of
C2, a precursor of C3.
C. C3 may be decreased due to a genetic defecl
lhat causes deficient production. In certain
autoimmune disorders, such as systemic lupus
erylhematosus, continual complemenl activation
leads lo low levels; however, susceptibility to
pyogenic infections is not a feature of autoimmune diseases. DiGeorge syndrome is a deficiency in T cells, and complement protein C2 is
not a precursor of C3
What is the predominant type of antibody
found in the serum of neonates born after
full-term gestation?
A. Infant IgA
B. Infant IgG
C. Infant IgM
D. Maternal IgG
D. Antibody production is immunogen induced.
Because the fetus develops in a sequestered site, it
makes very little immunoglobulin. Maternal IgG
crosses the placenta and is the primary antibody
found in infant’s circulation.
An important part of the nonspecific
immune response is(are)
A. B cells
B. Basophils
C. Complement cascade
D. Cytotoxic T lymphocytes
C. Important parts of an animal’s nonspecific
immune response include phagocytosis, inflammation, and complement activation. In a nonspecific immune response, the animal responds in
much Ihe same way to all invaders. B cells and
cytoloxic T lymphocytes responded to specific
antigens and are, therefore, involved in the specific immune response. Basophils are involved
in type I hypersensitivily reactions.
The major class of immunoglobulin found
in adult human serum is
A. IgA
B. IgE
C. IgG
D. IgM
C. Immunoglobulin G is Ihe predominant class
of immunoglobulin found in serum. It accounts
for approximately 80% of the lolal serum
immunoglobulin. The normal range is 800-1600
mg/dL.
Which class of immunoglobulin possesses
delta heavy chains?
A. IgA
B. IgD
C. IgE
D. IgG
B. The heavy chains divide human immunoglobulin molecules into separate classes and subclasses. The della (A) heavy chain corresponds to
IgD. The remaining classes IgA, IgE, IgG, and
IgM correspond to a, e, y, and JJL, respectively.
Which class of immunoglobulin possesses
10 antigenic binding sites?
A. IgA
B. IgD
C. IgG
D. IgM
D. The IgM molecule is a penlamer that contains 10 binding sites. However, the actual
valence falls to 5 with larger antigen molecules,
probably because of steric restrictions. IgA, IgG,
IgD, and IgE monomers each have two antigenic
binding sites.
Color Plate 22 * represents a dimeric IgA
molecule. The structure printed in red and
indicated by the red arrow is called the
A. J-piece
B. Hinge region
C. Heavy chain
D. Light chain
A. IgA is found in mucous secretions as a dimer
stabilized by the J-piece. IgA is synthesized
locally by plasma cells and dimerized intracellularly. IgM is also held together by a J-piece, but
il exists as a pentamer.
Which class of immunoglobulin binds to
basophils and mast cells to mediate
immediate hypersensitivity reactions?
A. IgA
B. IgD
C. IgE
D. IgG
C. Mast cells and basophils have surface receptors (FceRI) for the Fc portion of IgE. When IgE
molecules, attached to the surface of mast cells
and basophils, bind the allergen they are specific
for, this triggers the cells to degranulate, producing the symptoms of immediate type I hypersensitivity. The main function of IgE appears to
be the ability to trigger an immune response,
thereby recruiting plasma factors and effector
cells to areas of trauma or parasite infection
Type I hypersensitivity is
A. Associated with complementmediated cell lysis
B. Due to immune complex deposition
C. Mediated by activated macrophages
D. An immediate allergic reaction
D. Type I hypersensitivity reactions occur
immediately after second exposure to an allergen. On the first, or primary, exposure, IgE specific to the allergen is produced. The IgE binds
to Fc receptors on the surface of basophils and
mast cells. Immune complexes and complement
are not involved in the response
When performing the enzyme-multiplied
immunoassay technique (EMIT), how is
the ligand in the patient’s serum detected?
A. Agglutinates by binding to antibodycoated latex beads
B. Binds to enzyme-labeled antibody
C. Competes with enzyme-labeled
antigen for binding to a specific
antibody
D. Forms antibody-antigen complex and
precipitates
C. In the EMIT, a ligand (antigen) in a sample
competes with an enzyme-labeled ligand for
binding to a specific antibody. The labeled ligand is designed so that following antibody binding, the enzyme is inactive. As the ligand
concentration in the test sample increases, more
enzyme-labeled ligand remains unbound, resulting in greater enzyme activity.
Severe combined immunodeficiency
(SCID) is an
A. Immunodeficiency with decreased B
cells and neutrophils
B. Immunodeficiency with lymphocytopenia and eosinophilia
C. Immunodeficiency with decreased or
dysfunctional T and B cells
D. Immunodeficiency with decreased
lymphocytes and decreased complement concentration
C. SCID is defined as a condition in which
adaptive immune responses (i.e., cell-mediated
and humoral-mediated immune responses) do
not occur because of a lack of T and B cell activity. A number of genetic defects can lead to this
condition. Children born with SCID need to live
in a sterile environment, and they have a short
life expectancy
An example of immune injury due to the
deposition of antigen-antibody complexes is
A. Acute glomerulonephritis
B. Bee-sting allergy
C. Contact dermatitis
D. Penicillin allergy
A. Acute glomerulonephritis is caused by the
presence of a soluble circulating antigen (Ag) that
provokes and combines with antibody (Ab). As
these Ag-Ab complexes reach a critical size, they
are deposited in the glomerular membranes of the
kidney. Upon deposition, an acute inflammatory
reaction occurs because of complement activation.
Bee-sting and penicillin allergies are examples of
IgE-mediated anaphylactic reactions. Contact dermatitis is mediated by T cells, not antibody.
The serologically detectable antibody
produced in rheumatoid arthritis (RA) is
primarily of the class
A. IgA
B. IgE
C. IgG
D. IgM
D. Rheumatoid factor (RF) is an immunoglobulin
that reacts with antigenic determinants on an IgG
molecule. Although they may be of several types,
the one that is easily serologically detectable is
IgM. This is because of the agglutination activity
of the molecule. RF tests are commonly used in
the diagnosis of rheumatoid arthritis.
In bone marrow transplantation, immunocompetent cells in the donor marrow may
recognize antigens in the recipient and
respond to those antigens. This phenomenon is an example of
A. Acute rejection
B. Chronic rejection
C. Graft versus host disease
D. Hyperacute rejection
C. Bone marrow transplants by their nature contain immunologically competent cells: B cells
and T cells in particular. Unless the transplanted
marrow is HLA-matched perfectly to the donor,
the immunocompetent cells in the transplant will
recognize and react against the nonself HLAs of
the recipient’s tissues. This phenomenon is known
as graft-versus-host disease, because the graft
attempts to reject its host. Acute rejection, chronic
rejection, and hyperacute rejection are examples
of mechanisms a recipient’s immune system uses
to reject a graft.
Multiple myeloma is a
A. Lymphoproliferative disease of T cells
B. Cancer of plasma cells characterized
by increased antibody concentration
C. Lymphoproliferative disease resulting
in a decrease in antibody production
D. Cancer of monocytes characterized by
increased kappa and lambda chain
synthesis
B. Plasma cells are normally end-stage cells; they
live a few days and die. During multiple myeloma,
plasma cells become cancerous and continue to
secrete antibody. The cells also secrete excess
light chains that can be found in the urine; these
proteins are called Bence Jones proteins.
Which one of the following describes a
direct immunofluorescence assay?
A. Conjugated reagent antigen reacts with
antibodies to form antigen-antibody
complexes
B. Antigens react with unlabeled
antibody forming antigen-antibody
complexes that attach to labeled
antibodies
C. A dye is attached to a molecule and it
reacts with an immune complex to
produce a color
D. Conjugated reagent antibody reacts
with antigen to form antigen-antibody
complexes
D. In a direct imrnunofluorescence assay, a fluorescent molecule is linked to an antibody. This
complex is often called a conjugate. Clinical material is fixed onto a microscope slide, and the conjugate is added. After a wash step, the slide is
examined with a microscope using UV light. If
antigen specific to antibody was present in the
clinical specimen, fluorescence will be seen
In individuals allergic to pollen, hyposensitization protocols may be initiated.
These individuals receive injections of
A. Allergen
B. Pooled human antisera
C. Monoclonal antibody directed against
human T cells
D. Monoclonal antibody directed against
human B cells
A. Hyponsensitization, allergy injections, involves
the administration of gradually increasing concentrations of an allergen. The goal is for the
patient to become tolerant of the allergen and no
longer exhibit an allergic response to the allergen. It is hypothesized that patients will ultimately develop high concentrations of IgG to the
allergen, blocking IgE from binding and thereby
preventing the allergic reaction
After exposure to antigen, the first
antibodies that can be detected belong to
the class
A. IgA
B. IgE
C. IgG
D. IgM
D. The first B cells to respond to antigen differentiate into plasma cells that produce IgM antibody. Later in the immune response, stimulated
B cells undergo a phenomenon called “class
switching” and begin to produce antibodies of
the IgG, IgA, and IgE classes. High concentration of IgM in patient serum is indicative of a
recent infection
Corneal tissue may be transplanted
successfully from one patient to another
because
A. The cornea is nonantigenic
B. Cornea! antigens do not activate T cells
C. Anticorneal antibodies are easily
suppressed
D. The cornea occupies a privileged site
not usually seen by the immune system
D. Corneas are readily transplanted from one
individual to another. This is because the cornea
is nonvascularized and is a sequestered site.
Thus the immune system of the host does not
“see” the cornea and recognize it as foreign.
A kidney transplant from one identical
twin to another is an example of a(n)
A. Allograft
B. Autograft
C. Isograft
D. Xenograft
C. Identical twins have the same genetic makeup.
Grafts between them would be isografts or
syngeneic grafts. Autografts are transplantations from one site to another in the same individual.
Xenograft refers to transplantation between different species. Transplantation between two nonidentical individuals of the same species is called an
allograft.
In Bruton disease, measurement of serum
immunoglobulins would show
A. Elevated levels of IgE
B. Elevated levels of IgG
C. Normal levels of IgG and IgM but
reduced levels of IgA
D. The absence of all immunoglobulins
D. Bruton disease is a congenital form of agammaglobulinemia. It is a sex-linked phenomenon
that affects males. Because B cells are not produced, affected males have levels of IgA, IgD,
IgE, and IgM undetectable by routine assays.
IgG may be absent or present at very low levels.
Diagnosis of group A streptococci
(Streptococcus pyogenes) infection is
indicated by the presence of
A. Anti-protein A
B. Anti-DNaseB
C. Anti-beta-toxin
D. C-reactive protein
B. The serological diagnosis of group A streptococcal infection can be made by demonstrating anti-DNase B. The antistreptolysin O (ASO)
assay can also be used; however, ASO response
is poor in skin infections. C-reactive protein is
an acute-phase protein indicating inflammation.
A molecule found in human serum
sometimes used as a tumor marker is
A. a-Fetoprotein
B. HBsAg
C. Biotin
D. CDI
A. a-Fetoprotein (AFP) and carcinoembryonic
antigen (CEA) are oncofetal antigens that
become expressed after malignant transformation. Approximately 70% of patients with primary hepatoma have elevated levels of AFP.
However, the major use of determining AFP
levels is in monitoring patients undergoing
cancer treatment.
Which cell is the principal source of
interleukin 2?
A. Bcell
B. Tcell
C. Monocyte
D. Plasma cell
B. Interleukin 2 (IL-2) is a lymphokine produced
by activated T helper cells. IL-2 principally affects
T cells, including the cell that released IL-2, acting
on its target cells via the IL-2 receptor. This receptor is not present on resting cells.
Diagnostic reagents useful for detecting
antigen by the coagglutination reaction
may be prepared by binding antibody to
killed staphylococcal cells via the Fc
receptor of staphylococcal protein A. The
class of antibody bound by this protein is
A. IgA
B. IgD
C. IgG
D. IgM
C. Staphylococcal protein A binds only the IgG
class (subclasses IgGl, IgG2, and IgG4) of
immunoglobulin. Binding occurs via the Fc portion of the antibody molecule, leaving the Fab
portion available to bind antigen in an immunologic assay. Binding of the Fab portion to test
antigen causes agglutination of the staphylococcal cells (coagglutination).
A major advantage of passive immunization
compared to active immunization is that
A. Antibody is available more quickly
B. Antibody persists for the life of the
recipient
C. IgM is the predominant antibody class
provided
D. Oral administration can be used
A. In passive immunization, preformed antibody
is delivered to the recipient, making the antibody
available immediately. In active immunization, a
period of days is required before antibody production occurs. Passive immunity is short-lived,
in contrast to the possibly lifelong persistence of
actively induced antibody. Because passive
immunization involves the transfer of antibodies,
the oral route cannot be used—antibodies are
digested in the gastrointestinal tract. The antibodies administered by passive immunization consist
largely of the IgG class
The strength with which a multivalent
antibody binds a multivalent antigen is
termed the
A. Affinity
B. Avidity
C. Reactivity
D. Valence
B. “Avidity” is used to describe the strength of
binding between a multivalent antibody and multivalent antigen. “Affinity” describes the bond
between a single antigenic determinant and an
individual combining site. “Valence” refers to the
number of antigenic determinants on an antigen
How does the secondary humoral immune
response differ from the primary
response?
A. The lag phase (the time between
exposure to immunogen and production of antibody) is longer in the
secondary immune response.
B. IgM is the predominant antibody class
produced in the secondary immune
response.
C. The antibody levels produced are
higher in the secondary immune
response.
D. Cytotoxic T lymphocytes play an
important role in the secondary
response
C. The secondary immune response is characterized by the predominance of IgG over IgM. In
addition, because of the formation of memory
cells following the primary response, the secondary response occurs much more quickly and
strongly. This is the basis for immunization as a
protection against various infectious diseases.
Cytotoxic T lymphocytes are not involved in
humoral immunity.
After activation of the complement
system, leukocytes and macrophages are
attracted to the site of complement
activation by
A. Cl
B. C5a
C. C8
D. IgM
B. The complement-activation product C5a is
chemotactic for neutrophils and macrophages.
Neither Cl nor C8 (which occur in the plasma
before complement activation) possesses such
chemotactic properties. IgM antibody, although
capable of activating complement by the classical pathway, is not a chemotactic factor for
phagocytic cells.
The type of immunity that follows the
injection of an immunogen is termed
A. Artificial active
B. Natural active
C. Artificial passive
D. Innate
A. Active immunity follows exposure to an
antigen that stimulates the recipient to develop
his or her own immune response. Vaccines are
an example of artificial immunity in that the animal was exposed to the immunogen by the
actions of a healthcare provider (unnatural). Surviving infections can result in natural active
immunity. Protection is due to the formation of
memory cells
The type of immunity that follows the
injection of antibodies synthesized by
another individual or animal is termed
A. Artificial active
B. Natural adaptive
C. Artificial passive
D. Natural passive
C. Artificial passive immunity results following
the injection of antibody synthesized by another
individual or animal. This type of immunity is
only temporary but may be very important in
providing “instant” protection from an infectious agent before the recipient would have time
to actively synthesize antibody. The injected
antibodies are treated as foreign proteins and are
eventually cleared from the body
