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Chapter 16: Adaptive Immunity

1. The five distinctive characteristics of adaptive immunity are specificity, memory, diversity, self-recognition, and inducibility. Specificity means the immune response targets a particular antigen. Memory means the body responds faster and stronger the second time. Diversity means the immune system can recognize many different antigens. Self-recognition means it usually avoids attacking the body’s own cells. Inducibility means it activates only when needed.

2. B lymphocytes originate and mature in the bone marrow. They become plasma cells that make antibodies and memory B cells. T lymphocytes originate in the bone marrow but mature in the thymus. T cells help activate immune responses, kill infected cells, or regulate immunity.

3. The two categories are antibody-mediated immunity and cell-mediated immunity. Antibody-mediated immunity involves B cells and antibodies. Cell-mediated immunity involves T cells, especially helper T cells and cytotoxic T cells.

4. An epitope is the specific part of an antigen that an antibody or T-cell receptor recognizes and binds to. It can be found on proteins, polysaccharides, capsules, cell walls, viruses, toxins, or other foreign molecules.

5. An antigen is the entire foreign substance, while an epitope is the small specific region on that antigen that immune cells recognize. Types of antigens include proteins, polysaccharides, lipids, nucleic acids, toxins, viral particles, bacterial structures, and allergens.

6. Yes. A bacterial cell can have multiple specific antigens because it has many different surface structures, such as flagella, capsules, pili, cell wall proteins, and toxins. Each structure can contain different epitopes.

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8. Major histocompatibility complexes, or MHCs, are cell markers that display antigens to T cells. MHC I is found on almost all nucleated body cells and presents intracellular antigens to cytotoxic T cells. MHC II is found on antigen-presenting cells and presents extracellular antigens to helper T cells.

9. Antigen-presenting cells are cells that engulf pathogens, process antigens, and present antigen fragments on MHC II molecules. Examples include dendritic cells, macrophages, and B cells. Their function is to activate helper T cells.

10. A dendritic cell phagocytizes a pathogen, digests it, and places pieces of the antigen on MHC II molecules. The dendritic cell then presents the antigen to a helper T cell. If the T-cell receptor matches the antigen-MHC II complex, the helper T cell becomes activated.

11. An antibody is a Y-shaped protein made of two heavy chains and two light chains. The tips of the Y contain antigen-binding sites. The stem region helps determine the antibody class and can activate complement or bind to immune cells.

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14. Cytokines are chemical messengers released by immune cells. They help cells communicate, activate T cells and B cells, increase inflammation, attract immune cells, and regulate the strength of the immune response.

15. Helper T cells activate B cells, cytotoxic T cells, and macrophages. Cytotoxic T cells kill infected or abnormal body cells. Regulatory T cells slow down immune responses and help prevent autoimmunity. Memory T cells remain after infection and respond faster if the antigen appears again.

16. In helper T-cell activation, an antigen-presenting cell presents an antigen on MHC II. A matching helper T cell binds to it and receives costimulation. The helper T cell becomes activated, releases cytokines, and clones itself. These activated helper T cells then help B cells make antibodies.

17. Cytotoxic T cells are activated when they recognize antigen presented on MHC I. Helper T cells also assist by releasing interleukin-2, or IL-2. Activated cytotoxic T cells clone themselves and kill infected cells using perforin and granzymes.

18. The primary response happens the first time the body encounters an antigen. It is slower and produces fewer antibodies, mainly IgM first and then IgG. The secondary response happens when the same antigen appears again. It is faster, stronger, and longer-lasting because memory cells already exist.

Diagram:
First exposure → slow IgM/IgG response → memory cells form
Second exposure → rapid, strong IgG response → faster protection

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20. Breastfeeding gives the baby passive immunity because breast milk contains IgA antibodies. These help protect the baby’s mucous membranes from infections.

Chapter 17: Immunization and Immune Testing

1. Immunization began with early observations that exposure to mild disease could protect against severe disease. Edward Jenner developed the smallpox vaccine using cowpox. Louis Pasteur later developed vaccines for diseases such as rabies and helped advance germ theory and immunization.

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3. Common U.S. childhood/adolescent vaccines include hepatitis B, rotavirus, DTaP, Hib, pneumococcal, polio, influenza, MMR, varicella, hepatitis A, HPV, meningococcal, and Tdap.

4. Herd immunity happens when enough people are immune that a disease has trouble spreading. This protects people who cannot be vaccinated, such as babies, elderly people, pregnant people, or immunocompromised individuals.

5. Serological tests detect antigens or antibodies in serum. Precipitation tests detect soluble antigens. Agglutination tests show clumping of particles. Neutralization tests show whether antibodies can block a toxin or virus.

6. Direct fluorescent antibody tests use fluorescent antibodies to detect antigen directly in a patient sample. Indirect fluorescent antibody tests detect antibodies in the patient’s serum by using a fluorescent secondary antibody.

7. Point-of-care testing allows rapid testing near the patient instead of waiting for a lab. It helps diagnose infections quickly, begin treatment sooner, and limit disease spread.

Chapter 18: Immune Disorders

1. An allergy is an exaggerated immune response to a harmless antigen called an allergen.

2a. Hypersensitivity is an overactive or harmful immune response. Immunodeficiency is when the immune system is weak or unable to respond properly.

2b. Localized anaphylaxis affects a specific area, such as the skin or nose. Generalized anaphylaxis affects the whole body and can cause shock, airway swelling, and death.

2c. An allergen is a substance that triggers an allergic response. An antigen is any substance that can be recognized by the immune system.

3. Ingested allergens include peanuts, shellfish, milk, and eggs. Inhaled allergens include pollen, dust mites, mold, and pet dander. Injected allergens include bee venom, medications, and vaccines.

4. On first exposure, the immune system becomes sensitized and produces IgE antibodies. IgE attaches to mast cells and basophils. On later exposures, the allergen binds to IgE, causing degranulation and release of histamine and other chemicals.

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6. Cross-linking of IgE antibodies occurs, resulting in degranulation.

7. Histamine causes vasodilation, increased capillary permeability, swelling, redness, itching, mucus production, smooth muscle contraction, and bronchoconstriction.

8. Atopy is a genetic tendency to develop allergic conditions. Examples include hay fever, asthma, eczema, and food allergies.

9. A wheal and flare reaction appears as a raised, swollen, itchy bump surrounded by redness.

10. Generalized anaphylaxis is more severe because it affects the whole body and can cause airway swelling, low blood pressure, shock, and death.

11. Asthma is an example of respiratory anaphylaxis because it involves allergic narrowing of the airways. Hay fever is usually localized to the nose and eyes. Tuberculosis is an infection, not anaphylaxis.

12. An EpiPen can be life-saving because it contains epinephrine, which quickly opens airways, raises blood pressure, and reduces severe allergic symptoms.

13. Desensitization allergy shots expose the person to small, gradually increasing amounts of allergen. This helps reduce IgE response and increases tolerance over time.

14. Both involve antibodies attacking red blood cells and causing hemolysis. Hemolytic transfusion reactions occur when incompatible blood is transfused. Hemolytic disease of the newborn occurs when maternal antibodies attack fetal red blood cells.

15. Type O red blood cells have no A or B antigens. Type O can donate to A, B, AB, and O.

16. Type AB red blood cells have A and B antigens. Type AB can donate red blood cells to AB only.

17. Hemolytic disease of the newborn usually happens when an Rh-negative mother carries an Rh-positive baby. The mother makes anti-Rh antibodies that can attack fetal red blood cells in a later pregnancy. It can be prevented with RhoGAM.

18. Serum sickness is a systemic Type III reaction where immune complexes deposit in tissues, causing fever, rash, joint pain, and inflammation. The Arthus reaction is localized immune complex inflammation at the site of antigen exposure.

19. No. Type IV hypersensitivity is not mediated by B cells or antibodies. It is mediated by T cells and is delayed.

20. Poison ivy causes contact dermatitis because oils from the plant act as allergens. T cells respond after exposure, causing redness, itching, swelling, and blisters.

21. Immune tolerance means the immune system recognizes the body’s own cells as “self” and does not attack them. Autoimmune disorders occur when this tolerance fails.

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24. Transplant success depends on how closely donor and recipient histocompatibility antigens match. If the recipient’s immune system sees the graft as foreign, T cells and antibodies can reject it.

25. The four basic graft types are autograft, isograft, allograft, and xenograft.

26. Primary immunodeficiency is inherited or present from birth, such as SCID. Acquired immunodeficiency develops later due to infection, disease, drugs, malnutrition, or cancer treatment. HIV/AIDS is an example.

Chapter 26: Microbial Ecology and Microbiomes

1. Microbial ecology is the study of how microorganisms interact with each other and their environment. Biodiversity means the variety of organisms in an environment. Biomass means the total amount or mass of living organisms.

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3. Competition occurs when microbes fight for space and nutrients. Antagonism happens when one microbe harms another, such as producing antibiotics. Cooperation happens when microbes help each other, such as sharing nutrients or forming biofilms.

4. Bioremediation is the use of microorganisms to clean up pollutants, oil spills, sewage, or toxic chemicals. It is important because microbes can break harmful substances into less harmful materials.

5. The six chemical elements that make up most macromolecules are carbon, hydrogen, oxygen, nitrogen, phosphorus, and sulfur.