NR 507 Week 1 Exam Immune Response and
Hypersensitivity Questions and Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which component of the immune system provides the first line of
defense against invading pathogens?
A. B lymphocytes
B. T lymphocytes
C. Physical and chemical barriers
D. Plasma cells
Rationale: Physical and chemical barriers such as intact skin, mucous
membranes, stomach acid, tears, saliva, and normal microbiota
constitute the body's first line of defense. They prevent pathogens
from entering tissues before the innate or adaptive immune systems
are activated.
2. Which immune response is considered nonspecific?
,A. Adaptive immunity
B. Humoral immunity
C. Cell-mediated immunity
D. Innate immunity
Rationale: Innate immunity provides immediate, nonspecific
protection against pathogens regardless of previous exposure. It
includes physical barriers, phagocytic cells, complement proteins,
inflammation, and natural killer cells.
3. Which cell is primarily responsible for producing antibodies?
A. Macrophage
B. Neutrophil
C. Plasma cell
D. Natural killer cell
Rationale: Plasma cells are differentiated B lymphocytes specialized
for producing antibodies (immunoglobulins). These antibodies bind
specific antigens to neutralize pathogens or mark them for
destruction.
, 4. Which leukocyte is the most abundant in normal peripheral
blood?
A. Eosinophil
B. Basophil
C. Monocyte
D. Neutrophil
Rationale: Neutrophils account for approximately 50–70% of
circulating white blood cells. They are the first responders during
acute bacterial infections and eliminate pathogens through
phagocytosis and enzyme release.
5. Which immunoglobulin is the first antibody produced during a
primary immune response?
A. IgA
B. IgG
C. IgE
D. IgM
Rationale: IgM is the first antibody synthesized after initial antigen
exposure. It is highly effective at activating complement and provides
, early protection until class switching to IgG or other antibody classes
occurs.
6. Which immunoglobulin readily crosses the placenta?
A. IgA
B. IgM
C. IgE
D. IgG
Rationale: IgG is the only immunoglobulin that crosses the placenta,
providing passive immunity to the fetus and newborn against many
infectious diseases.
7. Which immunoglobulin is primarily found in secretions such as
saliva, tears, and breast milk?
A. IgG
B. IgM
C. IgD
D. IgA
Hypersensitivity Questions and Correct
Answers (Verified Answers) Plus Rationales
2026 Q&A | Instant Download Pdf
1. Which component of the immune system provides the first line of
defense against invading pathogens?
A. B lymphocytes
B. T lymphocytes
C. Physical and chemical barriers
D. Plasma cells
Rationale: Physical and chemical barriers such as intact skin, mucous
membranes, stomach acid, tears, saliva, and normal microbiota
constitute the body's first line of defense. They prevent pathogens
from entering tissues before the innate or adaptive immune systems
are activated.
2. Which immune response is considered nonspecific?
,A. Adaptive immunity
B. Humoral immunity
C. Cell-mediated immunity
D. Innate immunity
Rationale: Innate immunity provides immediate, nonspecific
protection against pathogens regardless of previous exposure. It
includes physical barriers, phagocytic cells, complement proteins,
inflammation, and natural killer cells.
3. Which cell is primarily responsible for producing antibodies?
A. Macrophage
B. Neutrophil
C. Plasma cell
D. Natural killer cell
Rationale: Plasma cells are differentiated B lymphocytes specialized
for producing antibodies (immunoglobulins). These antibodies bind
specific antigens to neutralize pathogens or mark them for
destruction.
, 4. Which leukocyte is the most abundant in normal peripheral
blood?
A. Eosinophil
B. Basophil
C. Monocyte
D. Neutrophil
Rationale: Neutrophils account for approximately 50–70% of
circulating white blood cells. They are the first responders during
acute bacterial infections and eliminate pathogens through
phagocytosis and enzyme release.
5. Which immunoglobulin is the first antibody produced during a
primary immune response?
A. IgA
B. IgG
C. IgE
D. IgM
Rationale: IgM is the first antibody synthesized after initial antigen
exposure. It is highly effective at activating complement and provides
, early protection until class switching to IgG or other antibody classes
occurs.
6. Which immunoglobulin readily crosses the placenta?
A. IgA
B. IgM
C. IgE
D. IgG
Rationale: IgG is the only immunoglobulin that crosses the placenta,
providing passive immunity to the fetus and newborn against many
infectious diseases.
7. Which immunoglobulin is primarily found in secretions such as
saliva, tears, and breast milk?
A. IgG
B. IgM
C. IgD
D. IgA
