C6.1: HOST DEFENSE MECHANISMS Flashcards
Ways in which the body protects itself from
pathogens
Host Defense Mechanisms
How does host defense mechanism happen?
If the enemy (pathogens) breaks through the
first line of defense, it will encounter and, it is
hoped, be stopped by the second line of defense.If the pathogens manages to break through and
escape the first two lines of defenses, there is a
third line of defense is ready to attack it.
What are the host mechanisms for the 1st line of defense
-Skin
-Mucous membranes
-Secretion of skin and mucous membrane
What are the host mechanisms for the 2nd line of defense
-Phagocytic leukocytes
-Antimicrobial proteins
-Inflammatory response
- fever
What are the host mechanisms for 3rd line of defense
-Lymphocytes
-Antibodies
-Memory cells
The sticky mucous that is produced by
______ with the mucous membranes
serves to ____
goblet cells; entrap invaders.
In the third line of defense, special proteins called
_____ are usually produced in the body in response
to the presence of foreign substances called _____.
antibodies; antigens
The _____, ________ and ____
of the skin inhibit the growth of pathogens
dryness, acidity (approximately pH 5.0 ) and temperature (< 37 ͦC )
serves as a nonspecific host defense mechanism
by flushing organisms from the pores and the surface of the
skin.
Perspiration
Perspiration also contains the enzyme,
____–, which degrades
peptidoglycan in the bacterial cells (especially Gram positive
bacteria.)
lysozyme
is a protein that binds iron, a
mineral that are required by all pathogens.
Lactoferrin
is an enzyme that produces superoxide radicals,
highly reactive forms of oxygen, which are toxic to bacteria.
Lactoperoxidase
present on the epithelial cells of the posterior nasal membranes, nasal sinuses, bronchi, and trachea sweep the trapped dust and microbes upward toward the throat where they are swallowed or expelled by sneezing/coughing
Cilia (mucociliary covering)
____in the mucous membranes may also be
involved in this mucociliary clearance mechanism.
Phagocytes
can be thought of as nonspecific host
defense mechanism, because thousands of bacteria are
removed from the oral cavity every time we swallow.
Swallowing of saliva
factors that protects the digestive
system from bacterial colonization
Digestive Enzymes
Acidity of the stomach (approximately pH 1.5
Alkalinity of the intestines
The ______, which is secreted by the liver into the small
intestine, lower the surface tension and causes chemical
changes in bacterial cell walls and membranes that make
bacteria easier to digest.
bile
is an interaction where resident
microbes of the indigenous microflora prevent the
colonization of new arrivals to a particular anatomical site.
Microbial antagonism
F actors that attributes to the inhibitory
capability of indigenous microflora
Competition for colonization sites
Competition for nutrients
Production of substances that kill other bacteria.
The _______
is a group of cells, tissues
and organs that work
together to protect the
body. This is the ____
second line of defense; immune
system
It is the Cornerstone of
Inflammation and Specific Immunity
Phagocytosis
The General activities of Phagocytes
*To survey the tissue compartments and discover
microbes, particulate matter;
*To ingest and eliminate these materials; and
*To extract immunogenic information (antigen) from
foreign matter
General purpose phagocytes
Neutrophils
These cells primarily attack bacteria. They are dispensable,
rather like pawns on a chessboard.
Neutrophils
They rush to the site of incoming bacteria to fight them, but
are easily killed.
Neutrophils
These cells are like the bosses.
T helper cells
They give instructions to other cells by
producing signals.
T helper cells
These are killer cells.
Cytotoxic (killer) T cells
They punch holes in the walls of the
pathogen cell so that the contents ooze out.
Cytotoxic (killer) T cells
means ‘big eater’.
Macrophage
These cells ‘eat’ (ingest) or clean up the mess of
dead cells.
Macrophage
These cells are like the spies.
Dendritric cells
They notice if there is an invader and then
present evidence of the invader to T cells in
the lymph nodes.
Dendritric cells
These produce antibodies, which lock onto the antigen of
invading bacteria and immobilise them until the
macrophage consumes them.
B cells
Some B cells become memory cells after being activated by
the presence of _______.
antigen
These cells are able to live for a long time and can respond
quickly following a second exposure to the same antigen.
B cells
When the infection is gone, the immune system
needs to be calmed down (or the killer cells may
keep killing).
Suppressor T cells
The ____slow down or turn off the
immune system to prevent damage to good cells.
Suppressor T cells
The lymphatic system is a
system of thin tubes that runs
throughout the body. These
tubes are called _____ . They contain ___.
lymph vessels; lymph
is fluid in which
white blood (immune) cells
are found.
Lymph
are small, round masses of tissue that are found
in certain areas (such as the neck, groin and armpits). They filter
Lymph nodes
They filter
bacteria and other foreign materials out of lymph and expose
them to B and T cells and macrophages that can engulf them.
Lymph nodes
It functions to store and delivered iron to the host cells.
Transferrin
A temperature greater than 37.5 ͦ C ( 100100ͦ F) is generally considered
.
fever
A glycoprotein synthesized in the liver, has a high affinity for iron
Transferrin
Fever can be ____ or ____
exogenous; endogenous
Substances that stimulate the production of fever is
called _________ which
may originated either outside or inside the body.
pyrogens or pyrogenic substance
Those form the outside of the body includes
pathogens and various pyrogenic substance that
produces or release _____
endotoxins
is an example of pyrogen
that is produced within the body (endogenous pryrogen)
Interleukin I (IL-1 )
Small, antiviral proteins produced by virus infected cells.
Interferons
What are the Three known types of interferon,
alpha ( α ), beta β ), and γ )
(α) interferon is produced by ________
B lymphocytes (B cells), macrophages,
and monocytes
(β) interferon is produced by
fibroblast and other virus infected cells
(γ) interferon is produced by
activated T lymphocytes (T cells) and natural
killer cells (NK cells)
localized physical condition in which part of the body becomes
reddened, swollen, hot, and often painful, especially as a
reaction to injury or infection
Inflammation
______begin when phagocytes move to
the site where they are needed. This directed migration is called _____ results of chemical attractants called ______
Phagocytosis; chemotaxis; chemotactic agent.
