Communication in living systems is normally not covered in the 10th grade biology curriculum. Because of this, you
should take the time to examine this topic. Chapter 43: The Immune System is our 2nd step in understanding this idea.
In this outline you will find the AP Bio curriculum that is addressed in chapter 43 and some questions that will guide you
so that you can begin to understand this topic.
Big Idea 2: Biological systems utilize free energy and molecular building blocks to grow, to reproduce, and to maintain
dynamic homeostasis

Enduring Understanding 2.D Growth and dynamic homeostasis of biological systems are influenced by changes
in the system’s environment
o Essential Knowledge 2.D.4 Plants and animals have a variety of chemical defenses against infections that
affect dynamic homeostasis
 Plants, invertebrates and vertebrates have multiple, nonspecific immune responses
 Invertebrate – nonspecific lacking pathogen-specific responses
 Plant – recognition systems with systemic responses, infection triggers chemical
response that destroy infected and adjacent cells = localizing effects
 Vertebrate – nonspecific and nonheritable defense against pathogens
 Mammals use specific immune responses triggered by natural or artificial agents that disrupt
dynamic homeostasis
 Cell mediated vs humoral responses
 Cytotoxic T cells – target intracellular pathogens when triggered by antigens displayed
on outside of cells
 B cells - produce antibodies
 Antigen/Antibody interaction
 2nd exposure to antigen – immune response
Big Idea 3: Living systems, store, retrieve, transmit and respond to information essential to life processes


Enduring Understanding 3.B Expression of genetic information involves cellular and molecular mechanisms.
o Essential Knowledge 3.B.2 A variety of intercellular and intracellular signal transmissions mediate gene
expression (11.1 and 11.4) (45.1 and 45.2)
 Signal transmission within and between cells mediates gene expression (11.4)
 Cytokines (43.1 immune response)
Enduring Understanding 3.D Cells Communicate by generating, transmitting and receiving chemical signals
o Essential Knowledge 3.D.2 Cells communicate with each other through direct contact with other cells or
from a distance via chemical signaling (11.1, 11.2, 45.1, 45.2)
 Cells communicate by cell-to-cell contact
 Immune Cells (43.2)
o Essential Knowledge 3.D.3 Signal transduction pathways link signal reception with cellular response
(11.2, 11.3)
 Many signal transduction pathways include protein modification (i.e. methylation of DNA) and
phosphorylation cascades (via a series of protein kinases)
o Essential Knowledge 3.D.4 Changes in signal transduction pathways can alter cellular responses (11.1,
11.2, 11.3, 11.4)
 Blocked or defective pathways = deleterious, preventative or prophylactic
 autoimmune disease (43.4)
 Drugs - antihistamines (43.4)
Use the information from chapter 43 (page 929) to answer the following questions.
1. Use figure 43.2 (page 930) to complete the table below.
Innate Immunity
Barrier Defenses:
Internal Defenses:
Adaptive Immunity
Humoral Response:
Cell-mediated Response:
2. We first encountered phagocytosis in Concept 7.5, but it plays an important role in the immune systems of both
invertebrates and vertebrates. Review the process by briefly explaining the 6 steps to ingestion and destruction
of a microbe by a phagocytic cell. (See figure 43.3 – page 930 of text.)
a.
b.
c.
d.
e.
f.
3. Explain the role of Toll receptor in producing antimicrobial peptides.
4. List the three defenses vertebrates share with invertebrates and the two defenses unique to vertebrates.
a. Similar:
i.
ii.
iii.
b. Unique:
i.
ii.
5. In the following chart, list five examples of barrier defenses and how they work.
Barrier Defense
How the Barrier Repels Pathogens
6. Explain how toll-like receptors are used in cellular innate defenses, using TLR3 and TLR4 as examples. (Use
figure 43.6 – page 932 of the text.)
a. TLR3
b. TLR4
7. In the chart below, explain the role of the four phagocytic cells.
Phagocytic Cell Type
Role in Innate Defense
Neutrophils
Macrophages
Dendrite cells
Eosinophils
8. Natural killer cells are not phagocytic. How do they assist in innate defenses and what type of cells do they
detect?
9. Trace the flow of lymph in the 4 stages found in figure 43.7 (page 933). For each stage, explain the role of the
lymphatic system in innate defense.
a.
b.
c.
d.
10. Explain the role of the following two antimicrobial compounds.
a. Interferon:
b. Complement:
11. Explain the inflammatory response using the three steps shown in figure 43.8 (page 934).
a.
b.
c.
12. It might seem like pathogens have little hope of mounting an infection, but do not forget that pathogens are
constantly evolving ways to circumvent our immune system. As examples, how do the pathogens that cause
pneumonia and tuberculosis avoid our immune responses?
13. From the first four paragraphs of section 43.2, summarize where T cells and B cells develop, and give an
overview of their functions. (Note that they are a type of white blood cell known as a lymphocyte.)
a. T cell
b. B cell
14. What is immunological memory, and why is it important?
15. Explain how cytokines help coordinate the innate and adaptive immune responses.
16. What is an antigen?
17. What is the relationship between an antigen receptor, an antibody, and an immunoglobin?
18. How is an epitope related to an antigen? (Look at 43.10 – page 936 in your text.)
19. Using figure 43.9 (page 935) draw a B cell and label the antigen-binding sites, light and heavy chains, variable
and constant regions, transmembrane region, and disulfide bridges.
20. What forms the specific antigen-binding site? (Be sure to recognize that each B cell produces only one antigen
receptor. For any one cell, all antigen receptors or antibodies produced are identical.)
21. Using figure 43.11 (page 936) draw T cell and label the antigen-binding site, alpha and beta chain, variable and
constant regions, transmembrane region, and disulfide bridge.
22. T cells also display only one receptor on the surface of the cell. Compare and contrast a T cell with a B cell.
23. B cell receptors recognize and bind to antigen whether they are free antigens (like a secreted toxin) or on the
surface of a pathogen. Explain the role of the major histocompatibility complex (MHC) to T cell receptor
binding.
24. Explain how a host cell uses the MHC to display antigens. (Figure 43.12 – page 937 in your text will help you to
answer this question.)
25. List four major characteristics of the adaptive immune system.
a.
b.
c.
d.
26. One of the early problems in immunology was trying to understand how an organism with a limited number of
genes (for humans, about 20,500) could produce a million different B cell protein receptors and 10 million
different T cell receptors! The answer resulted in a Nobel Prize and a stratling exception to the notion that all
cells have exactly the same DNA. Use figure 43.13 (page 938) to explain the four steps producing genetically
unique B cell receptors.
a.
b.
c.
d.
27. Explain how the body develops self-tolerance in the immune system.
28. Define the following terms:
a. Effector cells:
b. Memory cells:
c. Clonal Selection:
29. Using the blue text in the margin of Figure 43.14 (page 939), explain the three key events to clonal selection.
a.
b.
c.
30. Graphs similar to the one in figure 43.15 (page 940) have been seen on several AP Biology exams. It depicts the
primary and secondary immune response. The first arrow shows exposure to antigen A. The second arrow
shows exposure to antigen A again, and also antigen B. Label this graph and then use it to explain the difference
between a primary and secondary immune response.
a. Primary Immune Response:
b. Secondary Immune Response:
31. Explain fully the function of the two division of acquired immunity.
a. Humoral Immune Response:
b. Cell-Mediated Immune Response:
32. Helper T cells play a critical role in activation of both T cells and B cells. In full detail, label and explain the three
steps involved using figure 43.16 (page 941). This is an important step!
a.
b.
33. Explain the role of dendritic cells and macrophages in starting a primary and secondary immune response.
34. Explain the three steps that occur as a cytotoxic T cell destroys the target cell. (Use figure 43.17 – page 941 in
your text.)
a.
b.
c.
35. Explain the three primary steps that occur in B cell activation. (Use figure 43.18 – page 942 in your text.)
a.
b.
c.
36. What is the difference between plasma cells and memory cells produced from the activation of B cells?
37. Explain these three ways antibodies can dispose of antigens. (Use figure 43.19 – page 943 in your text.)
a. Viral neutralization:
b. Opsonization:
c. Activation of complement:
38. How do antibodies and natural killer cells work together to fight viral infections while the virus is inside the
body?
39. Using examples, explain the difference between active and passive immunity.
40. Describe how immunizations can serve as an example of active immunity.
41. Explain how monoclonal antibodies are used in home pregnancy kits.
42. Why is the antibody response to a microbial infection polyclonal?
43. Why is immune rejection an example of a healthy immune system?
44. What is the role of MHC in tissue and organ transplants?
45. What are allergies?
46. Use figure 43.22 (page 947) explain a typical allergic response.
47. Explain what happens if a person experience anaphylactic shock.
48. Autoimmune diseases occur when the immune system turns against particular molecules of the body. Describe
the cause and symptoms of the following autoimmune diseases.
a. Lupus:
b. Rheumatoid Arthritis:
c. Type 1 Diabetes Mellitus:
d. Multiple Sclerosis:
49. Explain how immunodeficiency diseases are different from autoimmune diseases.
50. Just as our immune system has evolved to thwart pathogens, pathogens have evolved to thwart our immune
system. Describe the following pathogen strategies.
a. Antigenic variation:
b. Latency:
c. Attach on the immune system (HIV):
51. Explain how the high mutation rate in surface antigen genes in HIV has hampered development of a vaccine for
AIDS. (You might take note that HIV – human immunodeficiency virus – is the virus that causes the disease AIDS
– acquired immunodeficiency syndrome. These acronyms are often used incorrectly.)