Host Defense, and Bacterial Pathogenicity and Virulence Flashcards
this is where mature B cells and T cells migrate to perfom their function
peripheral lymphoid organs
Infection as well as the development and progress of disease are related to 2 major factors which are
- Microbe’s virulence and pathogenicity
- Host’s immunity or resistance
This is a connective tissue cell which produces collagen and plays an important role in wound healing
fibroblast
Our ability to recognize and defend ourselves as well as to ward off disease caused by infectious agents or their products is called
Immunity or Resistance
Vulnerability or lack of immunity of the host to harm by infectious agents is referred to as
Susceptibility
What do we use to defend ourselves with when we are attacked by pathogens
Immune defense mechanisms
Two types of defenses involved in our immune defense mechanism
- non-specific defense
- specific defense
it is also known as natural, innate, native, and constitutive defense
non-specific defense
It provides a generalized protection against any foreign substance
non-specific defense
-it protects the body from any foreign substance however, it does not discriminate among them.
It provides a generalized protection against any foreign substance
non-specific defense
-it protects the body from any foreign substance however, it does not discriminate among them.
Specific defense is present at birth. T or F
False.
Non-specific defense
- It is present at birth hence the terms natural, innate, and native.
The non-specific defense is inherited as part of the structure and function of an individual. It only becomes active when exposed to foreign
substances.
False.
The non-specific defense is inherited as part of the structure and function of an individual. It is active and present even before exposure to foreign
substances. It is responds immediate and acts very fast.
Is non-specific defense enhanced by repeated exposure to the same foreign substance? Y or N
No.
What are the four mechanisms in the first line of defense?
- anatomic barriers
- physiologic barriers
- mechanical barriers
- host’s protective mechanism
It is the body’s protection at the site of entry of the foreign substance
First line of defense
It is a mechanism of the first line of defense which is characterized by physical barriers that prevent the entry and invasion of foreign substances. It consists of the intact skin and mucous membranes which line the respiratory tract, gastrointestinal tract, genito-urinary tract, and the conjunctiva.
anatomic barriers
These keep the vast majority of microorganisms out of the body by preventing microbial attachment
intact skin and mucous membranes (anatomic barriers)
Intact skin and mucous membranes keeps the vast majority of
microorganisms out of the body by preventing microbial attachment through several features like:
- epiglottis
- sphincters
- length of the male urethra
it is a flap of tissue that during swallowing, covers the opening leading to the lower respiratory tract
epiglottis
This prevents reflux of materials in the GIT (intestines) and GUT (unrinary bladder)
sphincters
a part of male genitalia which puts more distance between the bladder and the external source microbes
length of the male urethra
They function to prevent growth of microorganisms which are capable of passing the physical barrier
physiologic barriers (physiological secretions)
Physiologic barriers in the skin
- sebum
- sweat
- low pH
- low water
contains fatty acids which are antimicrobials
sebum (physiologic barriers)
consists of antimicrobial concentration of salts and lysozyme which dissolves peptidoglycan layer of bacteria.
sweat (physiologic barriers)
is a poor environment for microbial population
low pH (physiologic barriers)
content creates poor environment for proliferation
low water (physiologic barrier in skin)
What is the physiologic barrier found in respiratory tract
goblet cells that secrete mucus containing lysozyme
Physiologic barrier in gastrointestinal tract
gastric juice
- contains a mixture of hydrochloric acid, proteolytic enzymes, and mucus
- very acidic (pH 2-3), sufficient to destroy most organisms and their toxins
Physiologic barrier in genito-urinary tract
- Low pH of urine and vaginal secretions oppose growth of microbes
- secretion of this tract contain LYSOZYME
The first line of defense which consists of mechanisms that continuously remove microbes from attachment site.
mechanical barriers
The first line of defense which consists of mechanisms that continuously remove microbes from attachment site.
mechanical barriers
mechanical barrier where epithelial sloughing occurs
skin
-epithelial sloughing removes surface microbes
mechanical barriers found in the respiratory tract
- nasal hair
- ciliated mucosa
- neurological sensitivity of the nasal mucosa
- neurological sensitivity of the trachea
this is a mechanical barrier in the respiratory tract which traps particle in mucus
nasal hair
a mechanical barrier in the RT which traps particles in air mucous which is propelled out of the respiratory tract
ciliated mucosa
discharges particles from the upper respiratory tract through sneezing
neurological sensitivity of nasal mucosa
discharges particles from the lower RT through coughing
neurological sensitivity of trachea
what is the mechanical barrier in the GIT
peristalsis
-the rhythmic contraction of the intestine results to expulsion of unattached microbes out of the GIT
mechanical barriers in the genito-urinary tract
- flow of urine = flushes away microbes
- epithelial sloughing = sheds attached microbes
a first line of defense which involves microbial antagonism
host’s protective mechanism
it is the prevention of colonization of microbial pathogens by the normal flora of a given anatomic site
microbial antagonism
includes non-specific cellular and chemical responses to microbial invasion
second line of defense
refers to the ingestion of solid particles such as microorganisms or cellular debris by eukaryotic cells
Phagocytosis
-involves phagocytes which engulf and digest foreign substances
phagocytes include what type of cells
white blood cells
macrophages
also known as leukocytes
white blood cells (WBCs)
referred to as “professional phagocytes”
neutrophils and monocytes
-phagocytosis consists their primary function
this type of WBC sometimes perform phagocytosis
eosinophils
<0.5% of WBC
basophil
1-3% of WBC
eosinophil
3-7% of WBC
monocyte
55-90% of WBC
neutrophil
20-35% of WBC
lymphocyte
a process wherein leukocytes accumulate and adhere to the epithelial cells of blood vessel walls at the site of injury
margination
- this happens during early stage of inflammation
- leukocytes move from the blood stream by passage through the endothelium and enter tissues
this is the outward passage of blood cells through intact vessel walls
diapedesis
arrangement of the moving out of WBCs
1st: neutrophils
2nd: monocytes
3rd: lymphocytes
tissue cell counterpart of monocytes
macrophages
macrophages consitute the molecular phagocyte system (MPS). T or F
False. Mononuclear Phagocyte System
Macrophages are neither wandering nor fixed. T or F
False. Macrophages are either wandering or fixed.
They are distributed throughout the body
macrophages in CNS
Microglia cells
macrophages in lungs
dust cells (alveolar macrophages)
macrophages in the liver
kupffer cells
macrophages in the kidneys
mesangial cells
macrophages in bones
osteoclasts
Phagocytosis is a process that does not follow a certain chronological order. T or F
False. The process of phagocytosis proceeds in a step-wise manner
the process of phagocytosis
- chemotaxis
- adherence
- ingestion
- digestion
- elimination
the second line of defense involves
- phagocytosis
- inflammation
- chemical responses
the directional movement of cells in response to chemical stimulus.
chemotaxis
phagocytes use ___________ to move toward the chemical stimulus
pseudopods
chemotaxis is initiated by
chemotactic agents
- attract phagocytes
- include microbial products, components of damaged cells, chemicals released by leukocytes
the attachment of the phagocyte’s cell membrane to the surface of the material to be ingested.
adherence
2 types of adherence
unenhanced attachment
enhanced attachment
involves generalized recognition and attachment of phagocytes by way of its surface glycoproteins. Also known as opsonin-independent or non-opsonic
unenhanced attachment
unenhanced attachment involves
attachment of phagocytes by way of its surface glycoproteins to certain components of microorganisms such as peptidoglycan, teichoic acids,
lipopolysaccharide (LPS) and mannose which are not present in human cells.
also called opsonin-dependent or opsonic
enhanced attachment
enhanced attachment employ the process of
opsonization
- the microorganisms are coated with serum proteins collectively called
opsonins (antibodies such as IgG and IgM, and complement component C3b)
hence, there is an increase in the efficiency by which phagocytes ingest microorganisms
The phagocyte extends pseudopodia to surround the material and completely encloses the material within a membrane bound vesicle called phagosome
ingestion
In the process of digestion, during phagocytosis, a digestive vacuole called _____________ is formed by fusion of the
phagosome and lysosomes containing hydrolytic enzymes
After the formation of phagolysosome, lysosomes release their
contents, a process known as
degranulation
for most bacteria, digestion is completed in
10-30 minutes
The residual body — indigestible materials in the phagolysosome are released from the phagocyte by exocytosis, occurs under
elimination
a process wherein the phagolysosome fuses with the cell membrane and expels its contents.
exocytosis
functions of phagocytosis
-Killing invading microbes.
-Disposal of damaged and dying cells from spleen.
-Removal of tissue debris from repairing wounds.
-Removal of debris as embryonic tissues replace one
another.
-Removal of cancer cells.
-Suppression of the growth of spontaneously arising
tumors.
inflammation is from the latin word
inflammatio - to set on fire
an important nonspecific defense reaction to tissue injury, such as that caused by a pathogen, trauma or wound
inflammation
the immediate response of the body to injury or cell death.
acute inflammation
the immediate response of the body to injury or cell death.
acute inflammation
gross features of acute inflammation
cardinal signs rubor - redness calor - warmth dolor - pain tumor - swelling functio laesa - altered function
the inflammatory process also proceed in orderly fashion. T or F
True
inflammatory process
- vasoconstriction
- vasodilation
- cellular response
- tissue repair
This occurs for short period of time following injury and it is characterized by the release of chemical mediators present in the blood such as histamine and kinins
vasoconstriction
histamine is released by
activated mast cells, basophils, and platelets
histamine and kinins are released into the area of injury. These chemical mediators induce
vasodilation
increase in in diameter of blood vessels
vasodilation
vasodilation results in
- increased blood flow
- increased capillary permeability
increased blood flow allows influx of ___________ to the site of injury
- phagocytes
- oxygen
- nutrients
increased blood flow brings __________ and causes transfer of ___________ to the surface or site of injury.
redness (rubor), internal heat (calor)
result of vasodilation which is characterized by the separation of endothelial cells that line the capillaries.
increased capillary permeability
separation of endothelial cells allow the creation of gaps in between the cells which in turn causes leakage of blood fluid and molecules into the tissues, resulting in
swelling (tumor) and pain (dolor)
this includes the occurrence of phagocyte migration and phagocytosis during inflammation
cellular response
The phagocytes stick to the walls of the blood vessel in a process called
margination
the passing through of phagocytes through the gaps between endothelial cells after margination is called
diapedesis
cellular response occurs within______________ of tissue damage
1 hour
The phagocytes destroy invading microorganisms by
phagocytosis
phagocytes die after engulfing large number of microorganisms and damaged tissues, forming _________
pus
this is a collection of dead cells including neutrophils and macrophages and various body fluids
pus
pus may be pushed to the surface of the body and accumulate in an internal cavity thereby referred to as
abscess
tissue repair involves ___________
fibrobalst proliferation
this involves the secretion of hundreds of small, active molecules to regulate, stimulate, and otherwise control the various aspects of the host’s defense.
chemical response
involve in bacterial cell lysis
lysozyme
involved in bacterial cell lysis; inflammation.
complement
inhibit microbial growth by binding iron.
Lactoferrin & transferrin
Clearance of bacteria.
Fibronectin
Act with peroxide to cause lethal oxidation of cells.
peroxidase
Resistance to virus infections
Interferons
Causes fever; promotes activation of the immune system
Interleukins
this defense mechanism occurs when host barriers and non-specific defenses fail to control an infectious agent
third line of defense
this involves the immune system and the immune responses
third line of defense (specific defense)
the third line of defense is induced by
host’s exposure to a foreign substance (antigen)
antigens are also known as
immunogens
most antigens are
proteins or polysaccharides
specific regions on the antigens’ surface are called
antigenic determinants or epitopes
third line of defense responds directly only at the inciting antigen. Hence it has
specificity
The specific defenses (third line of defense) intensify by repeated exposure to antigens, hence, it has
memory
the capability of the host’s third line of defense to recall or remember a prior immune response to a given antigen which results in a heightened immune response
anamnesis or immunologic memory
2 major components of the immune system
- immune cells
- lymphoid organs
they consist of the lymphocytes and the monocyte-macrophage
immune cells or immunocytes
these cells make up 25 - 35% of white blood cells in the
blood.
lymphocytes
Only <1% of total lymphocyte population circulate in blood, the rest and spends most of its life in tissues. T or F
True
lymphocytes circulate alternating between blood stream and lymphatic channel. T or F
True
The lymphocytes circulating in blood are classified into three
- B cells (5-15%)
- T cells (70-80%)
- Natural Killer (NK) cells (15%)
agranulocytes which circulate in the blood
monocyte
tissue counterparts of monocytes.
macrophages
monocytes and macrophages function primarily in phagocytosis. However, only monocytes function in antigen presentation and cytokine production. T or F
False. Both of which function primarily in phagocytosis as well as antigen presentation and cytokine production.
sites of lymphocyte production or encounter between lymphocytes and antigens
lymphoid organs or tissues
lymphoid organs have two types
- primary lymphoid organs
- secondary lymphoid organs
known as central lymphoid organs consist of the bone marrow and thymus.
primary lymphoid organs
It is the source of all blood cells
bone marrow
bone marrow becomes the normal site of hematopoiesis starting from the 5th intrauterine month until birth. T or F
True
from birth up to 2-3 years of age, all bone marrow (red marrow) are
hematopoietically active
In adults, the red marrow is confined to the flat
bones (skull, clavicle, sternum) and proximal ends
of the long bones (humerus, femur). T or F
True
yellow marrow (fatty) begins to appear at
5-7 years old
the site of B cell development and maturation
bone marrow
a flat, bilobed organ in front of the chest,
behind the top of the sternum, above the heart.
thymus
the proportion of thymus generally increases with growth until old age. T or F
False. until 8-10 years of age, thereafter begins to atrophy
site of T cell development and maturation
Thymus
referred to as the peripheral
lymphoid organs,
secondary lymphoid organs
secondary lymphoid organs are most often the sites of interaction
between the immune cells and foreign antigen. it is also where lymphocytes are most abundant. T or F
True
secondary lymphoid organs consist of
lymph nodes
spleen
MALT
secondary lymphoid organs consist of
lymph nodes
spleen
MALT
a diffuse or organized lymphoid tissues found in the
mucosal lining of RT, GIT, tonsils and skin.
MALT (mucus-associated lymphoid tissue)
MALT is changed to GALT or BALT depending on its location. T or F
True
made of all the lymphoid tissue found on the walls of the intestines (lymph
nodes, Peyer patches (ileum), isolated lymph follicles).
GALT (Gut-Associated Lymphoid Tissue)
made of all lymphoid tissue (tonsils, lymph nodes, lymph follicles) found in
the respiratory mucosae from the nasal cavities to the lungs.
BALT (Bronchial-Associated Lymphoid Tissue)
2 arms of the host’s immune response
- humoral immunity
- cellular immunity
this immunity is associated with production of antibodies (Abs)
humoral immunity
-due to this it is also called Antibody - Mediated Immune Response (AMI)
humoral immunity consists of activation of T cells and the antibodies they produce. T or F
False. B cells
B cell activation occurs through the process known as
clonal selection
Once a B cell becomes activated, it proliferates forming a clone of
cells specific to the same antigen. This called
clonal expansion
are responsible for anamnestic
response. They are long lived, and circulate more
actively.
memory B cells
secrete antibodies against the antigen that activated them. They only live a few days ( about 1 week)
plasma cells
secrete antibodies against the antigen that activated them. They only live a few days ( about 1 week)
plasma cells
are proteins that are made in response
to an antigen and can recognize and bind to that
antigen.
antibodies
antibodies are also known as
immunoglobulins
The simplest molecular structure of an
immunoglobulin
monomer
monomer consist of
four (4) polypeptide chains;
2 identical Light (L) chains and 2 identical Heavy (H) chains.
Treatment with protease separates the antibody
molecule in into two regions:
- fab regions
- Fc regions
also known as antigen-binding fragment
fab regions
-The Fab consists of the “arms” of the Y-shaped antibody
molecule.
also known as crystallizable fragment as it crystallizes at 4 degrees C
Fc region
he Fc region makes up the “stem” of the Yshaped anybody molecule. T or F
True
It is also responsible for
complement fixation, i.e., the binding of the
complement to antigen-antibody complex;
and the placental transfer of IgG
Fc region
5 classes of immunoglobulins
- IgG
- IgM
- IgA
- IgD
- IgE
Structure: Monomer Molecular weight: 150,000 Function: -Bacterial agglutination - Complement fixation - Opsonization -Toxin and viral Neutralization -Secondary immune response -Passive immunity for the newborns
IgG
Structure: pentamer molecular weight: 970,000 function: -Bacterial agglutination - Complement fixation - Opsonization -Toxin and viral neutralization - Primary immune Response
IgM
structure: dimer (with secretory component) molecular weight: 405,000 function: -Localized protection on mucosal surfaces.
IgA
Structure: Monomer Molecular weight: 175,000 function: -Serum function not known: presence on B cells functions in initiation of immune response.
IgD
Structure: monomer molecular weight: 190,000 function: -Allergic reactions; possibly lysis of parasitic worms.
IgE
This part of the antibody
molecule determines what will happen to the
antigen once they are bound together
the tail of the “Y”, the Fc region of the molecule
Fc region sa tail, Fab region sa parang pa v
functions of antibodies in host defense
- agglutination and precipitation
- opsonization
- toxin neutralization
- steric hindrance
- activation of the complement
- antibody-dependent cellular cytotoxicity
the reaction between
particulate antigens (cells such as bacteria)
and specific antibodies resulting into
clumping.
agglutination
the reaction between
soluble antigens and specific antibodies
forming aggregates.
precipitation
Clumping and/or aggregation enhances
phagocytosis. it also makes antigens
more readily phagocytosed than if they
were separate infectious units. T or F
True
clumping of bacteria causes immobilization/ T or F
True
clumping of bacteria causes immobilization/ T or F
True
play an
important role in the prevention or
recovery from infection caused by
encapsulated bacteria.
opsonins
Antibodies react with soluble bacterial toxin and block the active site of the toxin. This consequently blocks the interaction of the toxin specific target cell or substrate.
toxin neutralizer
Antibodies combine
with the surfaces of microorganisms and
block or prevent their attachment to
susceptible cells or mucosal surfaces.
steric hindrance
a defensive system
consisting proteins produced by the
h e p a t o c y t e s , l y m p h o c y t e s a n d
monocytes.
complement
It is named as such because it “complements” the
cells of the immune system and some
antibodies in destroying microbes.
complement system
i n s e r t s i n t o t h e m e m b r a n e o f
microorganisms or cells leading to loss of
osmotic integrity and lysis of the
targeted cell.
Cytolysis. C5b6789 complex (membrane attack complex, MAC)
C3b opsonizes
microorganisms and binds to the C3b
r e c e p t o r s o n p h a g o c y t e s s o
phagocytosis becomes more efficient.
opsonization
C3b opsonizes
microorganisms and binds to the C3b
r e c e p t o r s o n p h a g o c y t e s s o
phagocytosis becomes more efficient.
opsonization
a process in which immune cells, usually phagocytes, are attracted towards a factor. The C5a component of the complement is a potent chemotactic agent.
chemotaxis
a process in which immune cells, usually phagocytes, are attracted towards a factor. The C5a component of the complement is a potent chemotactic agent.
chemotaxis
C3a C 4 a a n d C 5 a a r e c o m p l e m e n t anaphylatoxins that stimulate mast cells and basophils to release histamine. These promote vasodilation and increased vascular permeability. An increased blood flow to the site of infection allows more complement, antibodies, and immune cells to enter the site of infection.
degranulation of mast cells
mediated by T cells which express specific T
cell receptors for antigens
cellular immunity
T cells are classified by glycoproteins on their surface called
clusters of differentiation
-membrane molecules that are especially
important for adhesion to receptors.
CDs of greatest importance
CD4 and CD8
-co-receptor molecules on
the surface T cells.
T cells are subdivided into 2 major functional classes
helper T cells
cytotoxic T cells
refers to the ability of a microbe to cause a disease in the host
pathogenicity
disease-causing microbes
pathogens
microorganisms that do not associate with their
host except in the case of disease. They cause disease even in normal (healthy)
individual.
True or obligate pathogens
are microbes that can cause disease only
when one or more of the defense mechanisms designed to restrict them from
the usually sterile internal tissues are breached by accident, by intent (eg,
surgery), or by an underlying metabolic or an infectious disorder (eg, AIDS).
Opportunistic or potential pathogens
refers to the degree of pathogenicity.
virulence
e the sum of characteristics that allow microorganisms to produce
disease in a host. These may be structural, biochemical, or genetic traits that are
determinants of virulence.
virulence factor
The ability of pathogenic bacteria to penetrate the host tissue
and spread encompasses mechanisms for colonization or overcoming host
defenses.
Invasiveness
bacterial surface structures or macromolecules that bind a
bacterium to a specific surface.
adhesins
bacterial extracellular substances (usually proteins, or
enzymes) which act locally — at a short range, in the immediate vicinity of
bacterial growth, that damage host cells and/or have the immediate
effect of facilitating growth and spread of the pathogen.
invasins
bacterial features which allow them to resist main line of
host defense against them such as the phagocytic and immune
responses of the host
aggressins
certain bacteria produce substances that
suppresses neutrophil chemotaxis.
inhibition of chemotaxis
Some bacteria have a
mechanism to cover their surface with a component which is seen
as “self” by host phagocytes, hence cannot be recognized.
Avoiding contact with phagocytes.
Some bacteria have a
mechanism to cover their surface with a component which is seen
as “self” by host phagocytes, hence cannot be recognized.
Avoiding contact with phagocytes.
certain bacteria possess
molecules that bind with Fc region of the antibody. The Fc region is
no longer available to bind with the Fc receptor on the
phagocytes, thereby inhibiting of opsonization.
Inhibition of phagocytic engulfment
Bacteria survive inside
phagosomes because they inhibit the fusion of the phagosome
with the lysosome thus prevents the discharge of lysosomal
contents into the phagosome environment.
Inhibition of phagolysosome formation
With some intracellular
microbes, phagosome-lysosome fusion occurs, but bacteria are
resistant to inhibition and killing by the lysosomal constituents.
Resistance to killing by lysosomal factors
occurs after contact with an immune stimulus
(antigen) that activates the B and T cells causing the body to
produce immune factors such as antibodies and immunereactive T cell
active immunity
occurs when the host receives immune
factors (e.g., antibodies) in immune serum that were
produced in the body of another individual or animal
donor
passive immunity
