Transcript Lecture 8

Branches of Microbiology •
Bacteriology •
Virology •
Mycology •
Parasitology •
Immunology •
Recombinant DNA technology •
• Vaccines & Vaccination
• Vaccines =are products produced from
microorganisms
• ### when introduced into a host
• ### stimulate immune system
• ### defense against particular microbial
disease
Immunology
Is a science dealing with immunity •
Immunity = the body’s defense against
particular pathogenic microorganism
Or •
= the ability to wardoff disease through •
body defenses
Susceptibility = lack of immunity •
Immunology
Immune system = is a set of mechanisms that •
protect an individual from infection , by
recognizing, killing, & eliminating foreign
pathogens or particle
Antigen(Ag) = any substance that causes •
antibody formation (=immunogen)
Antibody(Ab) = a protein produced by the body •
in response to an Ag & capable of combining
specifically with that Ag
•
Immunology
There are two types of immunity •
Innate immunity (non specific) = an •
individual genetically predetermined
resistance to certain disease
Adaptive immunity (specific) •
=immunity obtained during the life to
produce specific response
Innate immunity
Defenses that are present at birth •
The are always present & available to •
provide rapid responses to protect us
against diseases
First line •
Second line •
Innate immunity
Two components •
•
skin & mucous
membrane
First line of defense •
•
normal
microbiota
Innate immunity
•
phagocytosis
inflammation
Second line of defense
fever
Antimicrobial
substances
Innate immunity
first line of defenses
Skin & mucous membranes
Physical
factors ::
barriers to entry
or processes
that remove
microbes from
the body
surface
Chemical
factors ::
substances
made by the
body that inhibit
microbial
growth or
destroy them
(from a microbe’s persepctive)
The Body’s Surfaces
First line of defenses
skin & mucous membrane /Physical
factors
The skin is the most difficult surface to 
penetrate.
some microbes can penetrate mucous 
membranes but-------Saliva ----- washes microbes 
Respiratory tract– ciliary action remove 
microbes ---coughing & sneezing
First line of defenses
skin & mucous membrane / Chemical
factors
Oil glands of skin ---- inhibit the growth of •
microbes
Perspiration --- washes microbes •
Lysozyme (tears, nasal secretions, & •
perspiration)
High acidity of gastric juice – inhibit •
microbial growth in stomach
First line of defenses
Normal microbiota
Change the environment & prevent the •
growth of pathogens
## competing for essential nutrients •
## production of inhibitory substances •
that suppress the growth of potential
pathogen
First-Line Defense
Second line of defenses
If a microbe penetrates the first line of •
defense
phagocytosis
inflammation
fever
Antimicrobial substances
Second line of defenses
phagocytosis
Phagocytes = a cell capable of •
engulfing & digesting particles that are
harmful to the body
Phagocytosis = the ingestion of •
microorganisms by a cell
Second line of defenses
Phagocytosis
Phagocytes ==== WBC (=granulocytes, •
lymphocytes, monocytes)
## granulocytes (= neutrophils, basophils, •
eosinophils)
Leukocytes = White Blood Cells
Phagocytic Leukocytes
The mechanism of
phagocytosis
Second line of defenses
Phagocytosis
The mechanism of phagocytosis •
1– the phagocytes are attracted to •
microorganism
2—then adheres to microorganism •
•
## the adherence may be facilitated by •
Opsonization (= coating the
microorganism with serum proteins ==
opsonins==
Second line of defenses
Phagocytosis
3– pseudopods of the phagocytes engulf •
the microorganism & enclose it in a
phagocytic vesicle
4– the microorganisms are killed by •
lysosomal enzyme & oxidizing agent
inside the phagocytes
Second line of defenses
inflammation
**** a host response to tissue damage •
characterized by redness, pain, heat, &
swelling, & some time loss of function
Inflammation
Inflammation
Inflammation gives rise to localized reddening, swelling,
increased temperatures, and pain.

Inflammation
The function of inflammation is to localize tissue damage,
localize responses, and then to restore tissue function.
The action of localized leukocytes is enhanced via the 
attraction of neutrophils and monocytes normally found in
circulation.
Microbial materials such as LPS, flagellin (making up 
bacterial flagella), and even bacterial DNA serve as
indicators of infection which in turn activates the
production of pro-inflammatory cytokines (= immunesystem activating chemicals).
In addition to the cell-to-cell interactions underlying 
inflammation, the inflammatory response involves
localized increases in blood flow, leakage of blood vessels,
and attraction of leukocytes from the blood.

Second line of defenses
fever
*** is an abnormally high temperature •
produced in response to a bacterial or viral
infection
** fever is considered a defense against •
disease
Second line of defenses
fever
High body temp. •
** intensifies the effect of antiviral interferon •
** increases production of transferrins that •
decrease the iron available to microbes
Also high temp. •
** speeds up the body's reaction it may help •
body tissue repair them self's more quickly
** Ab. production have been shown to be •
enhanced at elevated temp.
Second line of defenses
antimicrobial substances
*** the body produce certain antimicrobial •
substances that lyse microorganism
*** the most important of these are the •
protein of the
Complement
& interferon
•
system
Interferon: An Antiviral
dsRNA normally is not present
in cells.
Complement system
*** it is a group of steps which composes •
a large number of components
= serum proteins which activated each •
other in a sub sequential manner)
to produce a specified •
action
destroy invading microorganism •
complement
Toll-Like Receptors
Danger, I’m infected!
signal.
Including
phagocyteattracting
cytokines.
Complement
1. Inactive
complement
proteins are
in constant
circulation.
3. These are the
consequences...
2. Complement
proteins are activated
by various mechanisms.
Adaptive immunity
Obtained during the life of the individual to •
produce specific response
**particular pathogen & antigen •
**it takes time in days •
**cell-mediated & humoral components •
**exposure leads to immunological •
memory
**lymphocytes, antigen-specific •
receptors & antibodies
Adaptive immunity
Cell-mediated response (immunity) •
Is based on T-cells (=type of lymphocytes) •
Humoral response (immunity) •
Is based on antibodies •
Adaptive immunity
Antigen (Ag) = immunogen
•
Ags = are the foreign particles which •
stimulate the immune system to secrete
antibodies
When Ag is introduced into the host, host cell •
induces the formation of specific antibody &
T-lymphocytes that are reactive against the
Ag (bacteria, viruses, pollen grains, dust…..)
Adaptive immunity
Immunogenicity •
Is the ability to induce a humoral & cell •
mediated immune responses
Adaptive immunity
Antibody (Ab) •
Abs = are proteins present on the •
surface of B-cells & secreted by plasma
cells
circulate in the blood where they search & •
kill the microbes
Abs reside on the serum •
Adaptive immunity
Adaptive immunity
each Ab molecule consists of 4 peptides •
chains-----2 identical heavy chains
-----2 identical light chains •
binds with disulphide bond •
The first a.a of both chains are highly •
variable from which it binds with the Ag
Adaptive immunity
Immunoglobulin classes •
5 classes based on the structure of their •
heavy chain constant region
IgG •
IgM •
IgA •
IgE •
IgD •
Adaptive immunity
== Is the most abundant class •
•
==Has the ability to cross the placenta (= •
provides a major line of defense against
infection for the newborn)
•
==complement activator •
•
==bind on phagocyte & mediate
•
opsonization
•
==neutralization of bacterial toxins •
IgG
IgM == the first immunoglobulin class •
produced in a primary infection or primary
response
== is the first immunoglobulin to be •
synthesizes by the neonate
IgA == it is the predominant •
immunoglobulin class in external secretion
(saliva, tears, breast milk & mucus of the
bronchial, genitourinary & digestive tract)
==it protect the external surfaces of the •
body from microbial attack (= prevent the
adherence of microorganism to the
surface of mucosal cells)
IgE == bind to mast cells & basophiles •
•
degranulation •
Histamine •
immediate
hypersensitivity
Hay fever & asthma •
hypersensitivity
IgD == involved with the differentiation of •
B-cells where it seems to be interacting
with Ag
Adaptive immunity
Active immunity=developed after •
Ag enter the body & the immune system
responds with Abs ##### long lasting
protection
or
•
Passive immunity=developed when •
Ab enter the body from an outside
source #### short lived protection
Passive immunity
Naturally acquired passive •
immunity (==immunoglobulin transferred
from mother to baby to protect the fetus
Or •
Artificially acquired passive •
immunity (==direct artificial injection of
Ab into the host)
Hepatitis Ig, serum containing antitoxin •
(tetanus)
Adaptive immunity
Active immunity •
Naturally acquired active immunity •
(==follows a short time illness)
) •
Or •
Artificially acquired active immunity •
(==vaccination)
Active immunity
illness
vaccination•
Active immunity
###memory cells in the lymphoid tissues are •
responsible for producing Ab ,the cells
remain active for many years & produce IgG
immediately after Ag entry (=secondary
immune response
Adaptive immunity
Humoral immunity (response) •
Is based on antibodies •
Cell-mediated •
immunity(response)
Is based on T-cells (=type of •
lymphocytes)
Humoral response
Abs bind to the Ag & facilitate their •
elimination
##forming clusters
ingested by
phagocytes
##binding of Ab to m.o. can activate •
complement system
lyses of m.o.
##Ab bind to toxins or viruses
prevent their binding to host cell
(neutralization)
•
Cell-mediated response
Based on T-cells = type of lymphocytes
T-cells are of 2 types
T-helper
&
T-cytotoxic
Cell-mediated response
When T-h interact with Ag molecule it •
becomes activated & begins to secrete
cytokines
activate B-cells
Ab
activate phagocytes
•
kill
activate T-c
kill •
cells that display pathogen (virus)
Autoimmunity •
Results from a loss of self-tolerance •
The ability of a host to recognize & •
not make Abs against self
Immune diseases === damage to ones •
own organs due to action of the immune
system
Rheumatoid arthritis =IgG, IgM & complement •
deposited in joints
severe pain •
Insulin dependent diabetes mellitus = •
destruction of insulin-secreting cells of the
pancreas=cell-mediated autoimmune reaction
Immunodeficiency === the absence •
of an adequate immune response
Congenital = inherited •
Or •
Acquired = drugs , cancers , infectious •
disease
•
AIDS
•
•
vaccination •
immunization •
the process of conferring immunity by •
administering a vaccine
Vaccines •
= are preparations of killed , inactivated or •
attenuated m.o or toxoids to induce
artificially acquired active immunity
Are the safest & most effective means of •
controlling infectious diseases
The effects of vaccination
The response of the body to the first •
contact with an Ag is called the primary
response , it is characterized by the
appearance of IgM followed by IgG
Subsequent contact with the same Ag •
results in a very high Ab titer & called the
secondary or memory response , the Ab
is primarily IgG
Attenuated ( living but weakened •
microbes)
Long life immunity •
Humeral & cell mediated response •
Reversion to virulence •
Inactivated (killed microbes) •
Short life immunity •
Antibody only •
Not reverse to virulance •
Subunit (antigenic fragments of microbes) •
Subunit •
Recombinant vaccines •
a cellular vaccines
bacterial cell
disrupted •
Vaccination program
1m 60d. 90d.
BCG
DTP
Polio.v
HiB
HBV
Measles
MMR
120d 10m
12 18-24 6y.
m m
*
*
*
*
*
IPV OPV OPV OPV
IPV
*
*
*
*
*
DT
OPV OPV
*
*
*
*
*
Polio vaccines
IPV =inactivated polio vaccine (killed) •
=== injection •
OPV = attenuated polio vaccine •
== orally •
intestine •
HiB = Haemophilus influenzae B •
== injection •
DTP = combination vaccines •
diphtheria •
tetanus •
pertusis •
== injection •
HiB + DTP === combination •
HBV = hepatitis virus type B = HBV •
surface antigen == biotechnology
BCG = tuberculosis •
== Bacillus Calmett-Guerin •
MMR = measles virus + mumps virus + rubella •
virus
Other vaccines •
Pox virus •
Cholera •
Chicken pox •
Influenza virus •
Endemic area •
Travelling to endemic area •
=== vaccines should not given to pregnant •
women
=== illness •
=== immunocompromized individuals •
Booster === to increase the power of •
effectiveness
Booster dose=== active immunizing agent
usually smaller than the initial dose given
to maintain immunity
•
Final Exam
Good Luck •