Quiz: Immunology Fundamentals — 9 questions

1. What is the primary role of antigens in the immune response?

A. They induce an immune response and are recognized by immune determinants.

B. They neutralize toxins without immune system involvement.

C. They produce antibodies.

D. They directly kill pathogens.

Answer: (A)

Explanation

Antigens are substances that induce an immune response and are recognized by specific immune determinants (epitopes). They are usually foreign, high molecular weight molecules like proteins or polysaccharides, which trigger the immune system to produce antibodies or activate immune cells.

2. Which immunoglobulin is primarily responsible for mucosal immunity and is present in secretions such as saliva and breast milk?

A. IgA

B. IgG

C. IgE

D. IgM

Answer: (A)

Explanation

IgA is the main immunoglobulin responsible for mucosal immunity and is found in secretions like saliva and breast milk, helping protect mucosal surfaces from pathogens.

3. Which immunoglobulin class is mainly responsible for mucosal immunity and is found in secretions like saliva and breast milk?

A. IgA

B. IgM

C. IgG

D. IgE

Answer: (A)

Explanation

IgA is the immunoglobulin class predominantly found in mucosal secretions such as saliva, tears, and breast milk. It plays a crucial role in mucosal immunity by preventing microbial attachment and invasion at mucosal surfaces, thereby protecting the host from infections.

4. Who first characterized immunoglobulins as glycoproteins with five classes?

A. Porter and Edelman in 1960

B. Küppers and Köhler in 1975

C. Kunkel and Edelman in 1959

D. Murray and Mahoney in 1982

Answer: (C)

Explanation

Kunkel and Edelman described immunoglobulins as glycoproteins with five classes in 1959, establishing a foundational understanding of antibody diversity.

5. In serological testing, what does the zone of equivalence signify in precipitation reactions?

A. The area where antigen is in excess.

B. The optimal ratio of antigen to antibody where visible precipitate forms.

C. The area where antibody is in excess.

D. The zone where no reaction occurs.

Answer: (B)

Explanation

The zone of equivalence is the optimal ratio of antigen to antibody in a precipitation reaction, where they are present in just the right proportions to form visible immune complexes or precipitates. This zone is essential for the detection and measurement of specific antigens or antibodies in laboratory tests.

6. What event can lead to a false negative in serological testing due to excess antibody?

A. Prozone phenomenon

B. Postzone phenomenon

C. Agglutination

D. Precipitation

Answer: (A)

Explanation

The prozone phenomenon occurs when excess antibodies prevent lattice formation, leading to false negatives in serological tests.

7. Which of the following is NOT characteristic of IgG?

A. Main serum antibody

B. Crosses the placenta

C. Activates complement

D. Neutralizes toxins

Answer: (B)

Explanation

While IgG can activate complement and cross the placenta, it does not primarily neutralize toxins; IgG neutralizes toxins via other mechanisms.

8. Which T lymphocyte subset is primarily responsible for killing infected cells?

A. Helper T cells (CD4)

B. Cytotoxic T cells (CD8)

C. B lymphocytes

D. Natural Killer cells

Answer: (B)

Explanation

Cytotoxic T cells (CD8) recognize processed antigens presented by infected cells and induce apoptosis, eliminating infected cells.

9. What is the primary function of IgE in immune responses?

A. Mucosal immunity

B. Allergic reactions

C. Complement activation

D. Opsonization

Answer: (B)

Explanation

IgE mediates allergic reactions by binding to mast cells and basophils, leading to histamine release upon allergen exposure.