AIDS, Addiction Quiz - ICSE Class 12 Biology

Free practice quiz: AIDS, Addiction (ICSE Class 12 Biology). 52 multiple-choice questions with answers and explanations. Play online, no sign-up needed.

Sample questions

1. Which of the following bacterial toxins acts as a superantigen, leading to massive T-cell activation and cytokine storm, often associated with severe food poisoning?

   1. Tetanospasmin
   2. Cholera toxin
   3. Toxic shock syndrome toxin-1 (TSST-1)
   4. Diphtheria toxin
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   Answer: C. Toxic shock syndrome toxin-1 (TSST-1)

   Toxic shock syndrome toxin-1 (TSST-1), produced by Staphylococcus aureus, is a potent superantigen. Superantigens bind to MHC class II molecules on antigen-presenting cells and the Vβ chain of T-cell receptors, bypassing normal antigen presentation and leading to massive polyclonal T-cell activation and a cytokine storm, characteristic of toxic shock syndrome.

2. The phenomenon where a vaccine can provide indirect protection to unvaccinated individuals when a sufficiently high proportion of the population is immune is called:

   1. Acquired immunity
   2. Active immunization
   3. Herd immunity
   4. Passive immunization
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   Answer: C. Herd immunity

   Herd immunity (or community immunity) occurs when a large percentage of a population is immune to an infectious disease, either through vaccination or previous infection. This makes the spread of the disease from person to person unlikely, thereby protecting individuals who are not immune (e.g., infants, immunocompromised individuals).

3. The inability of the immune system to distinguish between self and non-self antigens, leading to an attack on the body's own tissues, is the definition of:

   1. Immunodeficiency
   2. Hypersensitivity
   3. Autoimmunity
   4. Immunosuppression
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   Answer: C. Autoimmunity

   Autoimmunity is a condition where the immune system loses its tolerance to self-antigens and mounts an immune response against the body's own cells and tissues. This can lead to a variety of autoimmune diseases.

4. Immunological memory, which allows for a faster and stronger response upon re-exposure to an antigen, is primarily mediated by which type of lymphocytes?

   1. Plasma cells
   2. Regulatory T cells
   3. Memory B and T cells
   4. Dendritic cells
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   Answer: C. Memory B and T cells

   Following an initial encounter with an antigen, a subset of activated B and T lymphocytes differentiate into long-lived memory cells. These memory cells are primed to recognize the specific antigen. Upon subsequent exposure, they rapidly proliferate and differentiate into effector cells, leading to a more potent and swift secondary immune response.

5. The ability of a pathogen to cause disease is known as its:

   1. Infectivity
   2. Pathogenicity
   3. Toxicity
   4. Virulence
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   Answer: B. Pathogenicity

   Pathogenicity refers to the ability of a microorganism or pathogen to cause disease. Infectivity is the ability to enter and multiply in a host. Toxicity refers to the production of toxins. Virulence is the degree of pathogenicity, or the relative ability of a pathogen to cause disease.

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