CH 16 & 17 HOST DEFENSES
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Stephanie Lanoue
THE CONCEPT OF IMMUNITY
Learning Objectives
16-1 Differentiate innate and adaptive (acquired)
immunity.
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IMMUNITY
What is immunity exactly?
ability to ward off disease
What happens when we cannot ward off
disease?
Then we have susceptibility or the lack
of resistance to a disease. We can get
sick.
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BIG PICTURE: IMMUNITY AND LEVELS OF DEFENSE
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TYPES OF IMMUNITY

Innate immunity – _____ line of defense; defenses
against any pathogen; rapid, present at _______
Nonspecific defense mechanisms that come into play
immediately or within hours of an antigen’s appearance in
the body
 Includes physical barriers like skin, chemicals in the
blood, and immune system cells that attack foreign cells in
the body

Adaptive or acquired immunity – _______ line of
defenses; more _______ than innate immunity or
resistance to a specific pathogen; slower to respond,
creates immunological memory (the basis of
vaccination)
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DEFENSE MECHANISMS
The Immune system has __ lines of defense against
foreign pathogens
1. Physical and chemical barriers (falls under Innate Immunity)
2. Nonspecific Resistance (falls under Innate Immunity)
3. Specific Resistance (falls under Acquired Immunity)
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INNATE DEFENSE (FIRST LINE OF DEFENSE) PHYSICAL FACTORS





Cilia transports ________
trapped in mucus away
from the lungs
Earwax ________ microbes
from entering the ear
Urine cleans the urethra
via flow
Vaginal secretions move
microorganisms out of the
vaginal tract
Vomiting, diarrhea
Skin – dead cells in the
stratum corneum help protect
against pathogens; periodic
shedding of that stratum
removes microbes
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INNATE DEFENSE (FIRST LINE OF DEFENSE),
CONT - CHEMICAL FACTORS

Lysosomes (breaks cell walls) – tears, saliva, and sweat
glands (produce perspiration)

____________ microorganisms
Sebaceous glands on the skin produce oil, called _________
Moist hairs, protective film over skin
Fatty acid, pH 3 to 5, discourages growth of microbes
Gastric juice in the stomach destroys bacteria and most
toxins. HCL (chief component of stomach acid) provides a
very low pH 1 – 2.0
Saliva dilutes the number of microorganisms and washes
teeth and mouth
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INNATE DEFENSE (FIRST LINE OF
DEFENSE), CONT - NORMAL MICROBIOTA
 Normal
microbiota ___________ with
pathogens via microbial antagonism
Produce substances harmful to pathogens
 Alter conditions that affect pathogen survival

 Probiotics:
live microbial cultures
administered to exert a __________ effect
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BIG PICTURE: IMMUNITY
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INFLAMMATION
Learning Objectives
16-12 Describe second line defenses.
16-13 Describe inflammation; and the cause and
effects of fever.
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SECOND LINE OF DEFENSE – NONSPECIFIC
RESPONSE (INNATE IMMUNITY), CONT



Tissue damage triggers _______ defensive
responses
_______ signs and symptoms of infection: redness,
pain, heat, and swelling (edema)
Inflammation function:
Destroys injurious agent or limits its effects on the
body
 Repairs and replaces tissue damaged by the injurious
agent

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SECOND LINE OF DEFENSE – NONSPECIFIC
RESISTANCE (INNATE IMMUNITY), CONT.

Acute inflammation


Cause of inflammation flares ______ but is removed
rather quickly
Chronic inflammation

Cause of inflammation is difficult to remove, longer
period of time
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INFLAMMATION PROCESS
Vasodilation
1.

Vasodilation
Increase permeability of blood vessels
 Edema, accumulation of fluid
 Chemical such as histamine


Blood _____


Prevent microbes from spreading
Abscess

Dead cells and body fluid
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Figure 16.9a-b The process of inflammation.
Tissue damage
Bacteria
Epidermis
Blood
vessel
Dermis
Nerve
Subcutaneous
tissue
Vascular reactions and phagocytosis
Chemicals such as histamine,
kinins, prostaglandins,
leukotrienes, and cytokines
(represented as blue dots) are
released by damaged cells.
Blood clot forms.
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Abscess starts to form
(orange area).
INFLAMMATION PROCESS
Phagocyte migration and phagocytosis
2.



Phagocyte sticks to ______ surface of endothelium
_______ between endothelial cells of the blood
vessels o reach damaged area
Phagocytosis to destroy microorganism
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Figure 16.9b The process of inflammation.
Blood vessel
endothelium
Monocyte
Margination—phagocytes
stick to endothelium.
RBC
Bacterium
Diapedesis—phagocytes
squeeze between endothelial
cells.
Phagocytosis of
invading bacteria occurs.
Macrophage
Neutrophil
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Figure 16.9c The process of inflammation.
(c) Tissue repair
Scab
Blood clot
Regenerated epidermis
(parenchyma)
Regenerated dermis
(stroma)
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FEVER
Bacterial or viral infection
 Body, _____ temperature 39 ˚ C (102.2˚ F)
 Hypothalamus is normally set at 37°C (98.6 F)

Phagocytes release cytokine, cause hypothalamus increase
the temperature
 Constricting of blood vessels
 Increases metabolism rate

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SPECIFIC RESISTANCE (ADAPTIVE/ACQUIRED
IMMUNITY)

Relies on antigens (specific proteins found in foreign
microbes).
Antigens: substances that cause the production
of __________


Usually components of invading microbes or foreign
substances
Produces an immune response
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Major Types of Immune Cells
1. Cytotoxic T cells – these cells ________ cytotoxin
which triggers destruction of the pathogen’s DNA;
creates holes in the pathogens plasma membrane. The
holes cause the pathogen to lyse (rupture).
2. Helper T cells – these cells secrete interleukin which stimulates cell
division of ___ and B cells. In other words, these cells recruit even more
cells to help fight the pathogen.
3. Memory T cells – these cells remain dormant after the initial
exposure to an antigen. If the same antigen presents itself again, even
if its years later, the memory cells are stimulated to convert
themselves into cytotoxic T cells and help fight the pathogen
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FIGURE 17.1 DIFFERENTIATION OF T CELLS AND B CELLS.
Stem cells develop
in bone marrow or
in fetal liver
Stem cell
(diverges into
two cell lines)
Red bone
marrow
of adults
Thymus
Differentiate to
B cells in adult
red bone marrow
Differentiate to
T cells in thymus
T cell
B cell
Migrate to lymphoid
tissue such as spleen,
but especially lymph
nodes
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THIRD LINE OF DEFENSE, SPECIFIC DEFENSE,
CONT

The immune system distinguishes __ ______ of foreign
substances:

1 group consists of antigens that are _______ circulating in
the body (these include molecules, viruses and foreign
cells).

2nd group consists of ‘self’ cells that display proteins known
as MHC proteins (these proteins can originate from
antigens that have been engulfed and broken down or from
virus-infected and tumor cells that are actively
synthesizing foreign proteins
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SPECIFIC DEFENSE CONT.

Depending on the kind of foreign invasion, __ different
immune responses occur:
1. humoral (or _______ mediated response) –
involves__ cells that recognize antigens or
pathogens that are circulating in the lymph or blood
NOTE: “humor” is a medieval term for body fluid)
2. Cell mediated response – involves mostly __ cells and
responds to any cell that displays MHC markers,
including cells invaded by pathogens, tumor cells or
transplanted cells
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HUMORAL IMMUNITY CONT


Produces antibodies that combat foreign
molecules known as _________
B lymphocyte (B cells)
B cells develop from ____ bone marrow
 B cell receptors recognize antigens and make
antibodies
 Specific receptor for recognition of specific antigen

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ANTIGENS AND ANTIBODIES
 Antibody



Globulin proteins, immunoglobulin (Ig)
Response to ________
Recognize and bind to antigen
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CELLULAR IMMUNITY CONT

Cellular immunity (_____-mediated
immunity)

Produces ___ lymphocytes
Recognize antigenic peptides processed by phagocytic cells
 Mature in the thymus



T cell receptors (TCRs) on the T cell surface
contact antigens, causing the T cells to secrete
cytokines instead of antibodies
T cells response to intracellular pathogens

Best for fighting with viruses and some fungi
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Figure 17.20 The Dual Nature of the Adaptive Immune System.
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ADAPTIVE (ACQUIRED) IMMUNITY

___________


When a person exposed to microorganism and the
immune system responds
Passively

When antibody transferred from one person to
another
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Figure 17.18 Types of adaptive (or acquired) immunity.
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