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Chapter 43 Warm-Up
1. Define the following terms:
–
–
–
–
–
Pathogen
Antigen
Antibody
Allergen
Vaccine
2. What are lymphocytes? Where do B cells
and T cells mature?
Ch. 43 Review Warm-Up
1. What is the difference between innate
vs. adaptive immunity?
2. Contrast the functions of B cells and T
cells.
3. How are antigens recognized by
immune system cells?
4. What are memory cells?
5. How does HIV affect the immune
system?
Chapter 43
THE IMMUNE SYSTEM
What you must know:
• Several elements of an innate immune
response
• The differences between B and T cells
relative to their activation and actions.
• How antigens are recognized by immune
system cells
• The differences in humoral and cell-mediated
immunity
• Why Helper T cells are central to immune
responses
Types of Immunity
Innate Immunity
• Non-specific
• All plants & animals
Adaptive Immunity
• Pathogen-specific
• Only in vertebrates
• Involves B and T cells
Plant Defenses
• Nonspecific responses
• Receptors recognize pathogen molecules
and trigger defense responses
– Thicken cell wall, produce antimicrobial
compounds, cell death
• Localize effects
Figure 43.2
Pathogens
(such as bacteria,
fungi, and viruses)
INNATE IMMUNITY
(all animals)
• Recognition of traits shared
by broad ranges of
pathogens, using a small
set of receptors
• Rapid response
ADAPTIVE IMMUNITY
(vertebrates only)
• Recognition of traits
specific to particular
pathogens, using a vast
array of receptors
• Slower response
Barrier defenses:
Skin
Mucous membranes
Secretions
Internal defenses:
Phagocytic cells
Natural killer cells
Antimicrobial proteins
Inflammatory response
Humoral response:
Antibodies defend against
infection in body fluids.
Cell-mediated response:
Cytotoxic cells defend
against infection in body cells.
Antimicrobial Proteins:
Barrier Defenses:
• Interferons (inhibit viral
reproduction)
• Complement system (~30 proteins,
membrane attack complex)
•Skin
•Mucous membranes
•Lysozyme (tears,
saliva, mucus)
Innate
Immunity
(non-specific)
Natural Killer
Cells:
•Virus-infected and
cancer cells
Inflammatory Response:
• Mast cells release histamine
• Blood vessels dilate, increase
permeability (redness,
swelling)
• Deliver clotting agents,
phagocytic cells
• Fever
Phagocytic WBCs:
•Neutrophils (engulf)
•Macrophage (“big eaters”)
•Eosinophils (parasites)
•Dendritic cells (adaptive
response)
Phagocytosis
Inflammatory Response
Lymphatic System: involved in adaptive immunity
Adaptive Response
Lymphocytes (WBCs):
produced by stem cells in bone
marrow
• T cells: mature in thymus
– helper T, cytotoxic T
• B cells: stay and mature in
bone marrow
– plasma cells  antibodies
• Antigen: substance that elicits lymphocyte
response
• Antibody (immunoglobulin – Ig): protein made by
B cell that binds to antigens
Major Histocompatibility Complex (MHC)
• Proteins displayed on cell surface
• Responsible for tissue/organ rejection (“self” vs.
“non-self”)
• B and T cells bind to MHC molecule in adaptive
response
• Class I: all body cells (except RBCs)
• Class II: displayed by immune cells; “non-self”
Antigenpresenting
cell
Cell-Mediated Immune
Response
(T Cells)
Humoral Immune Response
(antibodies)
Helper T
cell
B cell
Cytotoxic T
cell
Plasma
cell
tag for
destruction
Antibodies
Infected
cell
Identify and
destroy
Immunological Memory
• Primary immune response: 1st exposure to antigen
• Memory cells:
– Secondary immune response: repeat exposure 
faster, greater response
Figure 43.14
B cells that
differ in
antigen
specificity
Antigen
Antigen
receptor
Antibody
Memory cells
Plasma cells
• Immunizations/vaccines: induce immune
memory to nonpathogenic microbe or toxin
• Passive immunity: via antibodies in breast milk
• Allergies: hypersensitive responses to
harmless antigens
• Autoimmune Diseases:
– Lupus, rheumatoid arthritis, Type I diabetes,
multiple sclerosis
• HIV: infect Helper T cells
– AIDS = severely weakened immune system