Biology Chapter 11: Innate Immunity Quiz

Chapter 11: Innate Immunity

• Innate immunity is a physiological process coordinated by the immune system to eliminate antigens.
• It's an inborn, ancient protection found in all eukaryotic organisms.
• Innate immunity is a generalized, non-specific response.
• Innate immunity's common features include recognizing diverse pathogens, eliminating identified invaders, and discriminating between self and foreign antigens.
• Adaptive immunity is found only in vertebrate animals and matures over time. It's specific to pathogens and requires 4-7 days to fully activate, longer than innate immunity.
• Adaptive immunity exhibits memory.
• Immune system is three collaborating lines of defense: barrier defenses, cellular and molecular defenses (Chapter 11), and adaptive defenses (Chapter 12)
• Normal microbiota have a role in shaping immune responses and conferring protection. These microbes fine-tune the immune system to fight pathogens and tolerate non-pathogens, food, and self-tissues.
• The hygiene hypothesis suggests a decrease in diversity and levels of microbes in the normal microbiota might negatively affect immune responses.
• Studies of germ-free animals show that environments without microbes lead to underdeveloped immune systems, and that normal microbiota have a direct role in immune system development.
• First-line defenses attempt to prevent pathogen entry. Subcategories include mechanical, chemical, and physical barriers.
• Mechanical barriers include flushing, rinsing, and trapping actions like tears washing debris, urine flushing microbes, saliva limiting adherence, and mucus membranes trapping microbes. The mucociliary escalator sweeps away microbes in the lungs.
• Chemical barriers directly attack invaders or establish environments that limit pathogen survival, such as lysozyme, stomach acid, and fatty acids.
• Antimicrobial peptides (AMPs) are proteins that destroy a wide spectrum of viruses, parasites, bacteria, and fungi.

Leukocytes Are Essential in All Immune Responses

• Leukocytes are classified as granulocytes (cells with granules visible when stained in their cytoplasm) and agranulocytes (cells lacking granules).
• Granulocytes include neutrophils, eosinophils, basophils, and mast cells.
• Agranulocytes include monocytes (which mature to macrophages) and dendritic cells.
• Lymphocytes (NK cells, B cells, and T cells) are approximately 25% of circulating white blood cells (WBCs).
  • NK cells are abundant in the liver and provide innate protection against viruses, bacteria, parasites, and tumor cells.
• T cells and B cells coordinate the adaptive immune response, more detailed in Chapter 12.
• White blood cell (WBC) counts (differential) diagnose infections if leukocytes are over- or underrepresented in a patient's blood.
• Examples of leukocytoses include neutrophilic leukocytosis (increase in neutrophils), eosinophilia (increase in eosinophils), basophilia (increase in basophils), monocytosis (increase in monocytes), and lymphocytosis (increase in lymphocytes).

Molecular Second-Line Defenses

• Cytokines are signaling proteins that allow communication between cells, initiating and coordinating immune actions. Increasingly used for diagnosis and therapy.
• Chemokines are a type of cytokine that attract white blood cells to areas of need.
• Interferons (IFNs) are signaling molecules that function when pathogens (especially viruses) or tumor cells are detected.
• Tumor necrosis factors (TNFs) are signaling proteins (primarily made by macrophages) that stimulate inflammation, kill tumor cells, and stimulate fever.
• Iron-binding proteins (like hemoglobin, ferritin, lactoferrin, and transferrin) limit iron availability to microbes. Some pathogens have evolved methods to steal iron from this defense.
• Complement proteins are >30 different proteins that work together in a cascade fashion. The system gets activated and enhances immune defenses.

Inflammation and Fever

• Inflammation is an essential part of innate immunity and healing in response to tissue damage.

• The three main goals of inflammation are recruiting immune defenses to injured tissue, limiting the spread of infectious agents, and delivering oxygen, nutrients, and chemical factors for tissue recovery.

• Cardinal signs of inflammation include redness, pain, localized heat (not fever), swelling, and loss of function.

• Inflammation occurs in three phases: vascular changes, leukocyte recruitment, and resolution.

• A fever is an abnormally high body temperature caused by pyrogens (e.g., toxins, cytokines.) which signals the hypothalamus to raise the body's baseline temperature.

• Studies suggest that fever enhances antiviral effects of interferons, increases phagocyte efficiency, enhances leukocyte production, limits pathogens, and promotes tissue repair.

• Low-grade fever (37.5°C to 38.3°C (99.5- 101°F)) is often considered protective.

• Antipyretics (such as aspirin, ibuprofen, or acetaminophen) reduce fever by limiting prostaglandin production in the hypothalamus. A fever that doesn't decrease with treatment above 40.5 °C (105°F) should be treated as an emergency.