Lecture AP Biology Chapter 43 The immune system

Chapter 43 Warm-Up
1. Define the following terms:
–
–
–
–
–

Pathogen
Antigen
Antibody
Allergen
Vaccine

1. 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
Innate
Immunity
Immunity

(non-specific)
(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:
cells mature in thymus
– helper T, cytotoxic T
•B cells:
cells stay and mature in
bone marrow
– plasma cells  antibodies


Antigen substance that elicits lymphocyte
• Antigen:
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:
I all body cells (except RBCs)
• Class II:
II displayed by immune cells; “non-self”


Antigenpresenting
cell

Cell-Mediated
Cell-MediatedImmune
Immune
Response
Response
(T
(TCells)
Cells)

Humoral
HumoralImmune
ImmuneResponse
Response
(antibodies)
(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
• Immunizations/vaccines:
memory to nonpathogenic microbe or toxin
immunity via antibodies in breast milk
• Passive immunity:
Allergies hypersensitive responses to
• Allergies:
harmless antigens
Diseases
• Autoimmune Diseases:

– Lupus, rheumatoid arthritis, Type I diabetes,
multiple sclerosis
HIV infect Helper T cells
• HIV:
– AIDS = severely weakened immune system