Download Non-Specific Host Defense Lecture

Purple bacteria
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Cyanobacteria
Actinomyces
www.ilstu.edu/~jbhelms
Gram-positive
Spirochetes
Escherichia Coli
Clostridium botulinum
Aquiflex
Mycobacterium tuberculosisi
Plantctomyies sp.
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Host-Parasite Relationships
Terms of Infectious Disease
Pathogen – Disease causing
Microorganism
Pathogenicity – Virulence
Infection – Invasion or colonization of body by a
pathogen
Disease – change from a state of health
Genus Bordetella (pertussis, parapertussis [whooping cough kills 100’s of thousands of children a
year world wide] and bronchiseptica)
PATHOGEN – Microbial parasite –
Outcome depends on
PATHOGENICITY – ability of the parasite (pathogen) to cause
damage to the host
AND the host
resistance or susceptibility to the parasite
Pathogenicity varies greatly among individual pathogens. The quantitative measure of pathogenicity
is VIRULENCE
VIRULENCE = expressed as the cell number (pathogens) that will elicit a
pathogenic response in the host within a given time period.
NEITHER Virulence nor relative resistance of the host are static. These items
change frequently. Interaction of the Host-Parasite is very dynamic..
Invasion by and multiplication of pathogenic microorganisms in a bodily part or tissue, which may
produce subsequent tissue injury and progress to overt disease through a variety of cellular or toxic
mechanisms.
the invasion of the body by pathogenic microorganisms and their multiplication which can lead to
tissue damage and disease
Disease – Also can be simply the damage or injury to the host that impairs host function caused by
pathogen
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Non-Specific Host Defense
Body Defenses Against Infections
Innate defenses – Non-Specific Defense
general defenses
protects against many pathogens
Adaptive defenses – Specific Defense - Acquired Host
Defense
immunity
more specific
carried out by lymphocytes
WHAT CAUSES INFECTION???
presence and multiplication of pathogens.
pathogen
disease causing agent
(bacteria, fungi, protozoans, parasites)
The body is equipped with two types of defense mechanisms to fight infection.
Nonspecific Resistance = protection against a wide range of pathogens. innate defenses OR
nonspecific resistance
general defenses
protects against many pathogens
Mechanisms include
species resistance,
mechanical barriers,
chemical barriers,
fever,
inflammation
phagocytosis.
adaptive defenses OR specific resistance
more specific
carried out by lymphocytes WHICH RECOGNIZE NONSELF ANTIGENS
immunity
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Non-Specific Host Defense
Body Defenses Against Infections
General Health and Physiological Condition –
Age, Sex, Race, Nutrition, and Occupation
Normal Flora –
Mutualistic and commensal microorganisms
Compete with Pathogens
Space and nutrient
Some produce antimicrobial substances
Can also alter pH and O2 availability
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In a healthy animal,
internal tissues, e.g. blood, brain, muscle, etc.,normally free of microorganisms.
Surface tissues, e.g. skin and mucous membranes, -- constantly in contact with environmental
organisms
become readily colonized by certain microbial species.
WRITE THIS ON THE BOARD ----------The mixture of organisms regularly found at any anatomical site is referred to as the normal flora
(Microbiota).
Normal flora of humans
exceedingly complex
consists of more than 200 species of bacteria.
Makeup of the normal flora depends upon various factors,
genetics, age, sex, stress, nutrition and diet of the individual.
DOWN TO HERE ---------The normal flora of humans consists of a few eukaryotic fungi and protists, and some methanogenic
Archaea that colonize the lower intestinal tract, but the Bacteria are the most numerous and
obvious microbial components of the normal flora.
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Non-Specific Host Defense
“The Heavy Seven”
Species Resistance
Mechanical Barriers
Fever
Chemical Barriers
Natural Killer Cells
Inflammation
Phagocytosis
Species resistance
Each species of organism is resistant to certain diseases that may affect other species, but
susceptible to diseases that other species may be able to resist.
Missing receptors or not as good a fit
Mechanical barriers (First Line of Defense)
skin and mucous membranes.
remain unbroken, they prevent the entrance of some pathogens.
tightly packed epithelial cells
Mucus membranes
Easier to penetrate than skin
Mucus traps particles
carry to nose and throat by cilia
respiratory epithelium
flow of body fluids (tears urine etc) carry microorganisms away
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Non-Specific Host Defense
“The Heavy Seven”
Species Resistance
resistance to certain diseases to which other
species are susceptible
Mechanical Barriers
skin
mucous membranes
Traps particles
Chemical Barriers
enzymes in various body fluids
pH extremes in stomach
high salt concentrations
interferons
defensins
collectins
Species resistance
Each species of organism is resistant to certain diseases that may affect other species, but susceptible to diseases that other
species may be able to resist.
Missing receptors or not as good a fit
Mechanical barriers (First Line of Defense)
skin and mucous membranes.
remain unbroken, they prevent the entrance of some pathogens.
tightly packed epithelial cells
Mucus membranes
Easier to penetrate than skin
Mucus traps particles
carry to nose and throat by cilia
respiratory epithelium
flow of body fluids (tears urine etc) carry microorganisms away
Chemical Barriers (First and Second Line of Defense)
Enzymes
pathogens.
enzyme in gastric juice (i.e pepsin) is lethal to many
enzymes in tears (i.e lysozyme) has
antibacterial action.
Acid
Low pH in stomach (hydrochloric acid)
prevents growth of some bacteria.
Salt
High salt concentration in perspiration kills
some bacteria.
Interferons
Interferon is a group of hormone-like peptides produced by certain uninfected cells in
response to the presence of viruses. Released from virus infected cells (lymphocytes and fibroblasts)
These antiviral proteins interfere with the proliferation of viruses, stimulate
phagocytosis, and enhance the activity of cells that help resist infections and the growth of tumors.
Defensins
Destroy bacteria by making holes in their cell walls and/or
membranes. Peptides produced by neutrophils and other granular WBC.
Collectins
Protect by attaching themselves to a variety of microbes. They
then are able to provide broad protection against them. Recognize sugar moieties on cell surface. Binds them and makes
the cells more easily phagocytized.
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Non-Specific Host Defense
Blood
Clot Plasma to remove fibrinogen and clotting factors left with SERUM – antibodies
and serum proteins
RBC == O2 transport
Platelets – blood coagulation
Lecukocytes (ALL WHITE BLOOD CELLS)
Granduloctyes
Basophils and Eosinophils == Hypersensitivity reactions and Inflammation
Neutorphils (PMN) Phagocytosis and Inflammation
Agranulocytes
Lymphocytes – B and T cells antibody synthesis and cell-mediated immunity
Monocytes – Phagocytosis – DIAPEDESIS
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Non-Specific Host Defense
“The Heavy Seven”
Inflammation
tissue response to injury
helps prevent spread of pathogen
promotes healing
blood vessels dilate
capillaries become leaky
white blood cells attracted to area
clot forms
fibroblasts arrive
phagocytes are active
Fever
inhibits microbial growth
increases phagocytic activity
Natural Killer Cells
type of lymphocyte
lysis of viral-infects
cells and cancer cells
Phagocytosis
neutrophils
monocytes
macrophages
destruction of
foreign particles
Inflammation:
Second Line Of Defense
NATURAL KILLER (NK) CELLS – small population of lymphocytes NOT associated with specific
response which secrete perforins. NK cells also secrete chemicals that enhance inflammation.
Inflammation is a tissue response to damage, injury, or infection.
Blood vessels dilate, increasing capillary permeability.
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The response includes localized tissue redness (erythema), swelling (edema), heat and pain .
Chemicals released by damaged tissues attract various white blood cells to the site of injury. NEUTROPHILS FIRST THEN
MONOCYTES!!
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Pus may form as wbc’s, bacterial cells, and debris accumulate.
Tissue fluid leaks into area.
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A clot (fibrin) may form in affected tissues.
Fibroblasts arrive.
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A fibrous connective tissue sac may form around the injured tissue and thus prevent the spread of
pathogens.
Phagocytosis:
Second Line of Defense
Definition: Phagocytosis is the process by which specialized cells engulf and ingest foreign particles in order to destroy
them.
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Recall function of lysosomes.
The most active phagocytes in the blood are neutrophils and monocytes.
Monocytes give rise to macrophages (through diapedesis, Chap 14) that migrate to various body tissues.
Phagocytic cells associated with the linings of blood vessels in the bone marrow, liver, spleen, and lymph nodes constitute
the reticuloendothelial tissue (MONONUCLEAR PHAGOCYTIC SYSTEM).
Phagocytes remove and destroy foreign particles from tissues and body fluids.
Fever
Infection (by bacteria and viruses) causes lymphocytes to proliferate and some then produce Interleukin I,(endogenous
pyrogen – “fire maker from within”) which increases body temperature.
Higher temp Liver and spleen sequester iron - But at higher temp microbes need more iron also.
Increased body temperature decreases blood iron levels, which increases phagocytic activity.
Other factors can also increase body temperature, including exposure to heat, UV light, acids, bases.
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Non-Specific Host Defense
Adherence
enhanced by opsoniation
adding of IgM and IgG molecules and C3b
Ingestion
phagosome
Digestion
pahgolysosome
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Non-Specific Host Defense
Intracellular Pathogens Can Survive Phagocytosis
Mycobacterium tuberculosis – TB and leprosy
Rickettsia rickettsii – Rocky Mt Spotted Fever
Chlamydia – venereal syndromes
Listeria monocytogenes -- listeriosis
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