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Microbiology

Immunology Practice Questions

20 free Immunology practice questions for the General Science. Tap an option to answer — you get instant feedback, the correct answer, and a detailed explanation for every question.

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Question 1 of 20 Medium

Which class of immunoglobulins is the only one capable of crossing the human placenta to provide passive immunity to the fetus?

  1. A IgA
  2. B IgE
  3. C IgG
  4. D IgM

Correct answer: IgG

IgG is the most abundant antibody in the serum and possesses a specific structure that allows it to be transported across the placenta. This provides the newborn with maternal protection during the first few months of life.

Question 2 of 20 Medium

Which type of immune cell is responsible for the production and secretion of specific antibodies?

  1. A Cytotoxic T cells
  2. B Plasma cells
  3. C Natural Killer cells
  4. D Macrophages

Correct answer: Plasma cells

Plasma cells are fully differentiated B lymphocytes that act as antibody factories. They produce large quantities of antibodies tailored to recognize the specific antigen that triggered the B cell activation.

Question 3 of 20 Medium

The 'Major Histocompatibility Complex' (MHC) Class I molecules are found on which of the following cells?

  1. A On B lymphocytes and macrophages only
  2. B On mature red blood cells only
  3. C On all nucleated cells in the body
  4. D On CD4+ T helper cells only

Correct answer: On all nucleated cells in the body

MHC Class I molecules are expressed by all nucleated cells to present endogenous antigens to CD8+ T cells. Red blood cells lack MHC Class I because they do not have a nucleus.

Question 4 of 20 Medium

Which of the following is considered a primary lymphoid organ, where lymphocytes undergo maturation?

  1. A Spleen
  2. B Lymph nodes
  3. C Peyer's patches
  4. D Thymus

Correct answer: Thymus

The primary lymphoid organs are the bone marrow (where B cells mature) and the thymus (where T cells mature). Secondary lymphoid organs, like the spleen, are where mature lymphocytes encounter antigens.

Question 5 of 20 Medium

What is the primary function of the 'Complement System' in the innate immune response?

  1. A To produce memory B cells for long-term immunity
  2. B To present processed antigens to T cells
  3. C To enhance phagocytosis and form membrane attack complexes
  4. D To secrete protective mucus that lines the respiratory tract

Correct answer: To enhance phagocytosis and form membrane attack complexes

The complement system is a cascade of proteins that opsonize pathogens for easier engulfment by phagocytes. It also culminates in the formation of the Membrane Attack Complex (MAC), which punctures bacterial cell walls.

Question 6 of 20 Medium

Which cytokine is primarily responsible for inducing an antiviral state in neighboring uninfected cells?

  1. A Interleukin-1
  2. B Tumor Necrosis Factor
  3. C Interferon
  4. D Histamine

Correct answer: Interferon

Interferons are cytokines released by virus-infected cells to alert nearby uninfected cells. Those neighboring cells then produce antiviral proteins that block viral replication if they are subsequently infected.

Question 7 of 20 Medium

In a Type I Hypersensitivity reaction (allergic reaction), which antibody isotype binds to mast cells and basophils?

  1. A IgD
  2. B IgG
  3. C IgE
  4. D IgM

Correct answer: IgE

IgE antibodies bind to high-affinity receptors on mast cells. Upon subsequent exposure to an allergen, the IgE molecules cross-link, triggering the release of inflammatory mediators like histamine.

Question 8 of 20 Medium

What is the role of 'Opsonization' in the immune process?

  1. A The direct neutralization of bacterial toxins
  2. B The movement of white blood cells toward a chemical signal
  3. C The programmed death of an infected host cell
  4. D The coating of a pathogen to promote its phagocytosis

Correct answer: The coating of a pathogen to promote its phagocytosis

Opsonization involves antibodies or complement proteins (like C3b) coating a microbe. This provides a 'handle' for phagocytes to bind to, significantly increasing the efficiency of ingestion.

Question 9 of 20 Medium

Which cell type is the primary target of the Human Immunodeficiency Virus (HIV)?

  1. A CD4+ T helper cells
  2. B CD8+ Cytotoxic T cells
  3. C Neutrophils
  4. D Eosinophils

Correct answer: CD4+ T helper cells

HIV binds to the CD4 molecule found on T helper cells. As these cells are destroyed, the immune system loses its ability to coordinate both humoral and cell-mediated responses.

Question 10 of 20 Medium

Naturally acquired active immunity is obtained through which of the following?

  1. A Vaccination
  2. B Breastfeeding
  3. C Recovery from an infection
  4. D Injection of preformed antitoxins

Correct answer: Recovery from an infection

Active immunity occurs when the individual's own immune system responds to a pathogen. 'Natural' refers to an environmental exposure (infection) rather than a medical intervention (vaccine).

Question 11 of 20 Medium

Which of the following is a hallmark of the 'Innate' immune system compared to the 'Adaptive' immune system?

  1. A It is highly specific to a particular strain of virus
  2. B It generates long-lasting immunological memory of pathogens
  3. C It involves the production of monoclonal antibodies
  4. D It responds immediately but non-specifically to pathogens

Correct answer: It responds immediately but non-specifically to pathogens

The innate immune system is the first line of defense and uses germline-encoded receptors to recognize broad patterns. It does not change with repeated exposure and lacks the memory found in the adaptive system.

Question 12 of 20 Medium

The 'Variable Region' of an antibody molecule is responsible for:

  1. A Binding to the Fc receptor on phagocytes
  2. B Determining the antibody class, such as IgG or IgA
  3. C Activation of the classical complement pathway
  4. D Binding to a specific epitope on an antigen

Correct answer: Binding to a specific epitope on an antigen

The variable regions (V-domains) at the tips of the 'Y' shape form the antigen-binding site. The unique sequence of amino acids in this region determines the specificity of the antibody for a particular antigen.

Question 13 of 20 Medium

Which white blood cell is typically the first to arrive at the site of an acute bacterial infection?

  1. A Neutrophil
  2. B Monocyte
  3. C Lymphocyte
  4. D Basophil

Correct answer: Neutrophil

Neutrophils are the most abundant leukocytes and are highly motile. They respond rapidly to chemotactic signals and are professional phagocytes that die after destroying bacteria, often forming pus.

Question 14 of 20 Medium

What is the function of 'Cytotoxic T Lymphocytes' (CTLs)?

  1. A To induce apoptosis in virally infected or tumor cells
  2. B To produce antibodies against extracellular bacteria
  3. C To phagocytize fungal spores
  4. D To dampen the immune response after an infection is cleared

Correct answer: To induce apoptosis in virally infected or tumor cells

CTLs (CD8+ T cells) recognize foreign peptides presented on MHC Class I molecules. They release perforins and granzymes to kill the target cell directly, preventing the spread of intracellular pathogens.

Question 15 of 20 Medium

DiGeorge Syndrome is a congenital disorder characterized by the absence of a thymus. Which immune function would be most severely impaired?

  1. A Macrophage phagocytosis
  2. B Production of complement proteins
  3. C Initial skin barrier function
  4. D T cell-mediated immunity

Correct answer: T cell-mediated immunity

Since the thymus is the site of T cell maturation, its absence leads to a profound deficiency in T cells. This severely compromises the cell-mediated immune response and the coordination of B cell responses.

Question 16 of 20 Medium

Which of the following is an example of an 'Autoimmune' disease?

  1. A Rheumatoid Arthritis
  2. B Severe Combined Immunodeficiency
  3. C IgA Deficiency
  4. D Acquired Immunodeficiency Syndrome

Correct answer: Rheumatoid Arthritis

Autoimmune diseases occur when the immune system loses self-tolerance and attacks the body's own tissues. In Rheumatoid Arthritis, the immune system targets the joints, causing chronic inflammation.

Question 17 of 20 Medium

The process by which white blood cells squeeze through the endothelial cells of blood vessels to enter tissues is called:

  1. A Chemotaxis
  2. B Opsonization
  3. C Apoptosis
  4. D Diapedesis

Correct answer: Diapedesis

Diapedesis, also called extravasation, is a critical step in inflammation. In response to chemical signals, leukocytes slow down, roll along the vessel wall, and then squeeze between endothelial cells into the site of injury or infection.

Question 18 of 20 Medium

Which of the following describes the 'Secondary' immune response compared to the 'Primary' response?

  1. A It is faster and produces mainly IgG antibodies
  2. B It develops slowly and produces mainly IgM antibodies
  3. C It is limited to mucosal surfaces
  4. D It lacks specificity for the original antigen

Correct answer: It is faster and produces mainly IgG antibodies

Due to the presence of memory B and T cells, the secondary response (on second exposure) has a shorter lag phase and a much higher magnitude. There is also an isotype switch from IgM to high-affinity IgG.

Question 19 of 20 Medium

MHC Class II molecules are primarily expressed by which group of cells?

  1. A Professional antigen-presenting cells
  2. B Neurons and glial cells
  3. C Hepatocytes in the liver
  4. D Skeletal muscle cells and cardiac myocytes

Correct answer: Professional antigen-presenting cells

APCs, such as Dendritic cells, Macrophages, and B cells, express MHC Class II. These molecules are used to present exogenous antigens (from captured microbes) to CD4+ T helper cells.

Question 20 of 20 Medium

Which component of the immune system is involved in 'Antibody-Dependent Cellular Cytotoxicity' (ADCC)?

  1. A Natural Killer cells
  2. B Complement C1 protein
  3. C Helper T cells
  4. D Red blood cells

Correct answer: Natural Killer cells

In ADCC, NK cells recognize the Fc portion of antibodies that are bound to the surface of a target cell. The NK cell then releases cytotoxic granules to destroy the antibody-coated cell.

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