Which of the following BEST describes the central event in identifying "nonself" molecules in the immune system? A) Phagocytosis of all foreign particles B) Molecular recognition via specific receptor binding to foreign molecules C) Fever response elevating body temperature D) Secretion of lysozyme into body fluids

B

What is the primary structural component of the insect exoskeleton that provides a barrier defense against pathogens? A) Cellulose B) Keratin C) Chitin D) Collagen

C

Which enzyme found in insect digestive systems destroys the cell walls of susceptible bacteria? A) Dicer-2 B) Argo C) Lysozyme D) Histamine

C

In the insect antiviral RNA defense mechanism, what does the enzyme Dicer-2 specifically recognize? A) Single-stranded viral RNA B) Double-stranded viral RNA formed during replication C) Viral capsid proteins D) CpG DNA sequences

B

After Dicer-2 cuts viral RNA into fragments, what is the role of the Argo protein complex? A) It destroys the host cell membrane B) It replicates the viral genome to exhaust resources C) It uses a single-stranded fragment as a guide to find and cut complementary viral mRNA D) It activates phagocytic cells in the bloodstream

C

Why can double-stranded RNA trigger an antiviral defense response in animals? A) Double-stranded RNA is inherently toxic to all cells B) Animals do not naturally produce double-stranded RNA, so its presence signals infection C) Double-stranded RNA activates the complement system directly D) Double-stranded RNA mimics bacterial flagellin

B

Which of the following correctly pairs a Toll-like receptor (TLR) with its ligand? A) TLR3 → lipopolysaccharide B) TLR4 → double-stranded RNA C) TLR5 → flagellin D) TLR9 → chitin

C

Which statement about TLR4 is correct? A) TLR4 is located inside vesicles and binds double-stranded RNA B) TLR4 is on the plasma membrane and recognizes lipopolysaccharide from bacteria C) TLR4 is a phagocytic cell that engulfs gram-negative bacteria D) TLR4 triggers adaptive immunity only

B

The discovery that mammalian immune cells use Toll-like receptors similar to the insect Toll receptor was awarded which prize? A) Nobel Prize in Chemistry, 2008 B) Nobel Prize in Physics, 2010 C) Nobel Prize in Physiology or Medicine, 2011 D) Nobel Prize in Physiology or Medicine, 2015

C

Which of the following correctly describes neutrophils? A) Large phagocytic cells that reside permanently in organs B) Cells that release histamine during inflammation C) Phagocytic cells that circulate in the blood and are attracted to infected tissue D) Cells that detect cancerous or virus-infected cells via abnormal surface proteins

C

A macrophage permanently stationed in the spleen would be MOST likely to encounter which type of pathogen? A) Pathogens entering through the skin B) Pathogens circulating in the blood C) Pathogens in inhaled air D) Pathogens in the digestive tract lumen

B

Which cell type is described as primarily populating skin and tissues that contact the environment and stimulates adaptive immunity? A) Mast cells B) Eosinophils C) Dendritic cells D) Natural killer cells

C

How do natural killer cells destroy virus-infected or cancerous cells? A) By engulfing them through phagocytosis B) By releasing chemicals that lead to cell death without engulfing them C) By releasing histamine to cause inflammation at the site D) By producing antibodies that tag the cells

B

Eosinophils are BEST suited for defending against which type of pathogen? A) Intracellular bacteria B) Enveloped RNA viruses C) Multicellular parasitic worms D) Gram-negative bacteria

C

Which cell type releases histamine during an inflammatory response? A) Neutrophils B) Macrophages C) Mast cells D) Eosinophils

C

What is the IMMEDIATE effect of histamine release during a local inflammatory response? A) It activates natural killer cells B) It causes nearby blood vessels to dilate and become more permeable C) It stimulates the bone marrow to release neutrophils D) It triggers the complement cascade

B

Which of the following correctly describes the sequence of events in phagocytosis? A) Lysosome fuses → vacuole forms → pseudopodia engulf → exocytosis of debris B) Pseudopodia surround → endocytosis → vacuole forms → lysosome fuses → toxic compounds destroy → exocytosis C) Endocytosis → pseudopodia surround → lysosome fuses → exocytosis D) Vacuole forms → pseudopodia surround → lysosome fuses → toxic compounds destroy

B

What is pus composed of? A) Viral particles, red blood cells, and excess mucus B) White blood cells, dead pathogens, and debris from damaged tissue C) Activated complement proteins and interferons D) Lymph fluid and antimicrobial peptides only

B

After a local inflammatory response, pus and excess fluid are absorbed into which system? A) The circulatory system via arterioles B) The lymphatic system C) The digestive system via the appendix D) The urinary system via nephrons

B

What is the function of lymph nodes in the immune response? A) They produce red blood cells for oxygen delivery to immune cells B) They contain macrophages that engulf pathogens in lymph and activate adaptive immunity C) They store interferons for systemic release during infection D) They produce mast cells that release histamine

B

Which of the following is an example of a SYSTEMIC inflammatory response? A) Swelling and warmth around a splinter B) Accumulation of pus at a wound site C) A severalfold increase in white blood cells in the bloodstream due to meningitis D) Dilation of capillaries near a minor cut

C

What is the life-threatening systemic condition caused by an overwhelming inflammatory response to severe bacterial infection? A) Crohn's disease B) Tuberculosis C) Septic shock D) Pneumonia

C

Septic shock is characterized by which combination of symptoms? A) Low fever, high blood pressure, increased capillary flow B) Very high fever, low blood pressure, poor blood flow through capillaries C) Normal temperature, widespread hemorrhage, high white blood cell count D) Localized swelling, pus formation, and lymph node enlargement

B

Which of the following describes the mechanism by which interferons protect uninfected cells? A) Interferons destroy viral particles in the bloodstream before they reach healthy cells B) Virus-infected cells secrete interferons that induce nearby uninfected cells to produce substances that inhibit viral replication C) Interferons activate the complement cascade to lyse virus-infected cells D) Interferons recruit macrophages to engulf viral particles

B

What technology is used to mass-produce interferons for medical treatment? A) CRISPR-Cas9 gene editing B) Polymerase chain reaction (PCR) C) Recombinant DNA technology D) Gel electrophoresis

C

The complement system consists of approximately how many proteins, and where are they found? A) 5 proteins, in lymph nodes B) 30 proteins, circulating in blood plasma in an inactive state C) 100 proteins, stored in mast cells D) 12 proteins, embedded in cell membranes

B

What is the outcome when the complement system is fully activated against a pathogen? A) The pathogen is coated and transported to the lymph nodes B) The pathogen's DNA is degraded by endonucleases C) Lysis (bursting) of invading cells D) The pathogen is encapsulated and rendered dormant

C

Streptococcus pneumoniae avoids destruction by phagocytes through which mechanism? A) It secretes interferons that disable macrophages B) Its outer capsule interferes with molecular recognition and phagocytosis C) It produces double-stranded RNA that overwhelms the Argo complex D) It produces enzymes that destroy lysosomes after being engulfed

B

How does Mycobacterium tuberculosis evade the immune system after being recognized? A) It forms a protective capsule that blocks TLR binding B) It produces toxins that kill macrophages on contact C) It resists breakdown after being engulfed and reproduces within host cells D) It mimics self-proteins so immune cells cannot distinguish it as foreign

C

What is the approximate annual global death toll from tuberculosis? A) 10,000 people B) 100,000 people C) Over 1 million people D) Over 5 million people

C

What is the primary mechanism by which antimicrobial peptides kill pathogens? A) Inhibiting pathogen DNA replication B) Disrupting pathogen membrane integrity C) Blocking pathogen ribosomes from synthesizing proteins D) Neutralizing pathogen toxins in the bloodstream

B

What is the pH range of human skin secretions, and why is this significant? A) pH 7–8; it is slightly alkaline, which prevents viral binding B) pH 3–5; acidic enough to prevent the growth of many bacteria C) pH 6–7; it is neutral, which maintains microbiome balance D) pH 1–2; extremely acidic to kill all surface microbes

B

What is the approximate pH of the stomach, and what is its role in innate defense? A) pH 5; inhibits bacterial cell wall synthesis B) pH 7; activates complement proteins in ingested fluids C) pH 2; kills most pathogens in food, water, and swallowed mucus before they reach the intestines D) pH 4; activates lysozyme in swallowed mucus

C

Which of the following BEST distinguishes adaptive immunity from innate immunity? A) Adaptive immunity uses phagocytosis; innate immunity does not B) Adaptive immunity is found only in vertebrates; innate immunity is common to all animals C) Adaptive immunity responds faster than innate immunity D) Innate immunity requires prior exposure to a pathogen; adaptive immunity does not

B

A researcher discovers a new bacterium whose outer surface lacks lipopolysaccharide and flagellin. Which TLRs would MOST likely fail to detect this bacterium? A) TLR3 and TLR9 B) TLR4 and TLR5 C) TLR3 and TLR4 D) TLR5 and TLR9

B

An insect larva is infected by an RNA virus. Which enzyme would be the FIRST to act in the host's innate antiviral defense? A) Lysozyme B) Argo C) Dicer-2 D) Complement protease

C

A patient with a genetic disorder lacks functional mast cells. Which aspect of the inflammatory response would be MOST directly impaired? A) Phagocytosis of bacteria by macrophages B) Secretion of cytokines that recruit neutrophils C) Histamine-mediated vasodilation and increased vascular permeability D) Production of interferons to limit viral spread

C

Crohn's disease and ulcerative colitis are examples of disorders caused by which underlying immune dysfunction? A) Insufficient innate immune response allowing chronic infection B) Unregulated inflammatory response disrupting intestinal function C) Overproduction of complement proteins causing tissue lysis D) Natural killer cell dysfunction allowing tumor growth

B

Which of the following is a correct statement about the lymphatic system's role in immunity? A) Lymph is pumped by the heart through lymphatic vessels B) Lymphatic vessels return lymph to the blood via ducts draining into veins near the shoulders C) The lymphatic system produces all phagocytic cells used in immune defense D) Lymph nodes synthesize interferons and release them into the blood

B

A fever can be beneficial during infection for which of the following reasons? A) It directly kills pathogens by denaturing their proteins before the immune cells can respond B) It may enhance phagocytosis and accelerate tissue repair by speeding up chemical reactions C) It permanently shuts down complement protein activation to prevent septic shock D) It stimulates mast cells to release additional histamine

B