Pathogens and defense Knowledge-Based Download PDF

Questions

1. 1.

   During a localized inflammatory response initiated by tissue damage and pathogen entry, what is the direct physiological effect of histamine released by activated mast cells?

   • A) It causes local vasodilation and increases capillary permeability, facilitating the movement of fluid and phagocytes into the damaged tissue.
   • B) It binds directly to bacterial cell walls to assemble transmembrane pores that trigger osmotic lysis.
   • C) It stimulates helper T lymphocytes to differentiate immediately into plasma cells that secrete neutralizing antibodies.
   • D) It enters uninfected host cells and degrades viral genomic material before replication can occur.
2. 2.

   Which of the following describes the primary role of memory B cells during a secondary exposure to an identical pathogen?

   • A) They nonspecifically engulf circulating pathogens through receptor-mediated phagocytosis.
   • B) They rapidly proliferate and differentiate into plasma cells that produce large quantities of high-affinity antibodies.
   • C) They synthesize and secrete circulating complement proteins to assemble lytic membrane attack complexes.
   • D) They release cytotoxic granules containing perforin and granzymes to directly destroy extracellular virions.
3. 3.

   How do cytotoxic T lymphocytes eliminate host cells infected by an intracellular pathogen such as a virus?

   • A) They recognize viral peptides displayed on surface MHC class I molecules and secrete cytotoxic proteins that induce apoptosis.
   • B) They engulf the infected host cell via receptor-mediated phagocytosis and degrade it within intracellular phagolysosomes.
   • C) They synthesize and secrete soluble antibodies that bind to the infected host cell surface for destruction by erythrocytes.
   • D) They release histamine and heparin to directly dissolve the outer lipid membrane of the intracellular virus.
4. 4.

   Which of the following best describes how the process of opsonization aids in defending the human body against bacterial pathogens?

   • A) Antibodies or complement proteins coat the pathogen surface to facilitate its recognition and ingestion by phagocytes.
   • B) Cytotoxic T cells directly inject perforins and granzymes through the bacterial cell wall to induce cellular lysis.
   • C) Memory B cells rapidly divide into plasma cells that secrete digestive enzymes directly into the bloodstream.
   • D) Histamines released by mast cells chemically degrade the peptidoglycan layer of bacteria to cause osmotic collapse.
5. 5.

   Which of the following statements correctly distinguishes the human innate immune response from the adaptive immune response?

   • A) Innate immunity produces specific memory cells after primary exposure, whereas adaptive immunity provides generalized chemical barriers.
   • B) Innate immunity depends on clonal selection of antigen-receptor-bearing lymphocytes, whereas adaptive immunity relies exclusively on rapid phagocytosis.
   • C) Adaptive immunity acts as the immediate first line of defense during an infection, whereas innate immunity requires several days to become fully activated.
   • D) Innate immunity mounts an immediate, generalized defense without forming immunological memory, whereas adaptive immunity develops a targeted response against specific antigens and produces long-lasting memory cells.