AP Biology
Ch. 43 Immunity
We are born with part of our immune system (Innate
immunity) and acquire immunity throughout our lives. Use
the chart to help organize your learning.
Innate Immunity:
Rapid responses to a broad range of microbes
External
skin:



physical barrier
acidic pH of oil and sweat deters germs (pH: 3-5)
normal “flora” or growth release acids and metabolic waste to
deter germs

hairs filter
mucous membrane:

mucous

cilia
secretions:

stomach acid (exception: Hepatitis A)

enzymes in sweat, tears, saliva (lysozyme)
INTERNAL
Inflammatory Response: Chemical signals from damaged cells start
these responses:

> blood flow:
attracts phagocytic WBC; causes

> leakiness:
redness, heat, and swelling. Initiated by
histimine (stored in mast cells until triggered by injury.
Mrs. Loyd
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Internal
Lymphatic System:
A network of fluid-collecting vessels and organs, including the lymph
nodes that fight infection.
Consists of:

adenoids,

tonsils

lymph nodes

spleen

Peyer’s Patches’ on intestines

appendix
p901
Phagocytic cells: Natural Killer (NK) Cells
WBC:

Phagocytes: macrophages-phagocytosis

cause lysis of invaders
Antimicrobial Proteins

complement: 30 serum proteins naturally attack microbes
directly or by impeding reproduction (lysozyme).

interferon: natural defense against viral infections

defensins: secreted by activated macrophages
Mrs. Loyd
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ACQUIRED IMMUNITY
Slower responses to specific microbes
Most pathogens (invaders) are destroyed by phagocytes (nonspecific)
but are tagged as “non-self” by the binding of antibodies (specific).
THE IMMUNE SYSTEM
Immune system: Main line of defense

Recognizes “self” from “non-self.”

System must be primed by presence of antigen to work.

Defensive cells and antibodies are specific for an antigen.
Definitions:
Antigen: foreign substance (antibody generating)
Antibody: specific defense protein
Immunity: ability of system to “remember” previous
antigens and respond promptly on the next exposure.
Active Immunity:

antibodies enter naturally or artificially. Body produces antibodies in its own defense.
Passive Immunity: antibodies intro. From outside
Temporary Immunity (few weeks>months)

Ex. Mother > placenta > baby

Ex. Antibody injections for traveling.
THE IMMUNE RESPONSE
Acquired Immunity
Lymphocytes carry out the immune response

The immune response is used when pathogens get past
the first line of defense.

It takes several days after invasion before the immune
response is activated.

B-cells provide the humoral immune response.

B-cells are the main killers, attacking the enemy most
directly. They secrete antibodies, proteins that attack foreign
antigens in body fluids.

T-cells provide the cell-mediated response. They attack
infected body cells or stimulate defense by other cells.

Long-term immunity results from the memories of
enemies held by certain T-cells and B-cells.
Mrs. Loyd
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Antibodies




The structure of an antibody enables it to recognize and
bind to a certain antigen and trigger its destruction.
(abbrev: Ig)
Antigens activate only lymphocytes with complementary
receptors, a process called clonal selection.
In the primary response (see figure) the selected
lymphocytes multiply into clones of effector cells and
memory cells.
Memory cells mount a rapid secondary immune response
upon subsequent exposures.
Helper T cells and cytotoxic T cells are the main effectors of
the cell-mediated immune response.
When a helper T cell encounters an antigen-presenting cell, it
releases signals that activate itself and cytotoxic T cells and
help to stimulate B cells. Cytotoxic T cells attack infected body
cells that display foreign antigens attached to self proteins.
Mrs. Loyd
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Immune System Failure

Cancer is uncontrolled cell division. The immune system
normally destroys cancer cells before they spread.

HIV causes the immune system to fail by invading and
destroying helper T-cells and macrophages.

HIV and AIDS (6:51min)

Autoimmune and immunodeficiency diseases result when
the immune system turns against some of the body’s own
molecules. example: Lupus, Hemolytic Anemia

Allergies are hypersensitive responses to antigens
(allergens) that produce uncomfortable inflammatory
responses.

anaphylactic shock: a whole-body, life-threatening
reaction that can occur within seconds of exposure to an
allergen.

examples: people extremely sensitivity to:

bee venom, penicillin, peanuts, fish, spider bites

Death may occur within a few minutes

Individuals with known hypersensitivity carry
syringes containing the hormone epinephrine,
which counteracts this allergic response.
1. IgE antibodies produced in
response to initial exposure
to an allergen bind to
receptors on mast cells.
Mrs. Loyd
2. On subsequent exposure
to the same allergen, IgE
molecules attached to a
mast cell recognize and bind
the allergen.
3. Degranulation of the cell,
triggered by cross-linking of
adjacent IgE molecules, releases
histamine and other chemical,
leading to allergy symptoms.
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