Transcript STUDY OF IMMUNITY. NON

STUDY OF IMMUNITY. NON-SPECIFIC
RESISTANCE
1. Immunity. Types of immunity
2. Innate immunity. Mechanism of innate immunity
IMMUNITY
•
The
resistance
offered by the host
to the harmful effect
of
pathogenic
microbial infection
is called immunity.
Immunity
against
infectious diseases
is of different types.
IMMUNITY
ACQUIRED
ADAPTIVE
INNATE
Active
Passive
Artificial
Natural
Artificial
Natural
Specific
Non specific
INNATE IMMUNITY
•
This is basic immunity, which may be
genetically passed on from one
generation to other generation
•
It does not depend on prior contacts
with microorganisms
•
It may be non-specific when it indicates
a degree of resistance to all infection
•
It is specific when it shows resistance to
particular pathogens
The differences between Non-specific
Immunity and Specific Immunity
Non-specific Immunity
Specific Immunity
Response is antigenindependent
Response is antigendependent
There is immediate
maximal response
There is a lag time between
exposure and maximal
response
Not antigen-specific
Antigen-specific
Exposure results in no
immunologic memory
Exposure results in
immunologic memory
INNATE IMMUNITY
• Species immunity: Individuals of same
species show uniform pattern of susceptibility
to different bacterial infection.
• Racial immunity: Within a species different
races show differences in susceptibility to
infection.
• Individual immunity: Individual in population
shows variation in their response to microbial
infections. Factors influencing level of innate
immunity in an individual are: age; hormonal
influence; nutrition.
DEFENSE MECHANISMS
OF BODY
• Epithelial surfaces: the
intact skin and mucous
membrane covering the
body
confers
on
it
considerable
protection
against bacteria. They
provide mechanical barrier.
They
also
provide
bactericidal secretions.
• Tissue
defenses:
If
barrier
of
body
is
overcome
by
the
organisms, a number of
factors in normal tissue
and body fluid, play their
role.
Tissue factor may be divided
into:
•
Humoral factors - the body fluids and
organized tissues of human organism
naturally contain a variety of antimicrobial
agent that kill or inhibit the growth of
microbes. The sources and activities of a
variety of host antimicrobial substances are
summarized in the next slide
•
Cellular factors
Humoral factors
Substance
Common
Sources
Chemical
Composition
Activity
Lysozyme
Serum, saliva,
sweat, tears
Protein
Bacterial cell lysis
Complement
Serum
Proteincarbohydrate
lipoprotein complex
Cell death or lysis of
bacteria; participates in
inflammation
Basic proteins and
polypeptides
(histones,lysins and
other cationic proteins,
tissue polypeptides)
Serum or
organized tissues
Proteins or basic
peptides
Disruption of bacterial
plasma membrane
Lactoferrin and
transferrin
Body secretions,
serum, organized
tissue spaces
Glycoprotein
Inhibit microbial growth
by binding iron
Peroxidase
Saliva, tissues,
cells (neutrophils)
Protein
Act with peroxide to
cause lethal oxidations
of cells
Fibronectin
Serum and
mucosal surfaces
Glycoprotein
Clearance of bacteria
(opsonization)
Interferons
Virus-infected cells,
lymphocytes
Protein
Resistance to virus
infections
Interleukins
Macrophages,
lymphocytes
Protein
Cause fever; promote
activation of immune
system
MICROBIAL ANTAGONISM
• This refers to the protection of the
surfaces afforded by an intact normal flora
in a healthy organism
E.coli bacteria (yellow)
in the gut are part
of the normal intestinal
flora of humans
Phagocyte
attacks bacteria
•
Phagocytosis: Natural defense against
invasion of blood and tissue by bacteria or
others foreign particles are mediated by
phagocytic cell which ingest and destroy
them
PHAGOCYTOSIS CELLS MAY BE:
•
•
Microphages, e.g. polymorphonuclear
leucocytes.
Macrophages:
histocytes,
fixed
reticuloendothelial cells; monocytes.
Phagocytosis,
a
phagocyte (blue)
engulfing a yeast
cell (yellow)
The process of phagocytosis
consist of:
•
•
•
•
The first phase involves the approach of the
phagocyte to the microbe by means of positive
hemotaxis
In the second phase absorption of the
microorganism on the surface of the phagocyte
take place
The third phase is characterized by
submergence of the microbe into the phagocyte
In the fourth phase intracellular digestion of the
engulfed microbes by the phagocytosis take
place
Phagocytosis by a Macrophage
The neutrophils can form Neutrophil Extracellular Traps
(NETs). Once triggered, the cells undergo a novel
program leading to their death. While they perish, the cells
release the content of their nuclei. The nucleic acid,
mingled with bactericidal enzymes, forms a lethal network
outside the cell. Invading bacteria and pathogenic fungi
get caught and killed in the NETs
Neutrophil
granulocytes
have trapped
Shigella bacteria
in NETs
(Neutrophil
Extracellular
Traps)
Cilia: The ciliary escalator propels
trapped particles out of the respiratory
tract
Cilia in the trachea rhythmically beating
NON-SPECIFIC IMMUNITY
• Inflammation: Tissue injury or irritation initiated
by entry of bacteria or of other irritant leads to
inflammation
• Fever: It is natural
defense mechanism.
It may actually destroy
the infecting organism.
Fever stimulates the
production of interferon
and helps in recovery
from virus infections
COMPLEMENT SYSTEM
• Complement can be considered as part of
the constitutive host defense mechanisms
because of its role in inflammation and
phagocytosis.
• Complement is well known for its ability to
react with wide variety of antigen antibody
combination
to
produce
important
physiological results.
• At present complement is known to have 9
distinct components (C1-C9), making a total
of 20 proteins.
Important physiological effects of
complement system
•
•
•
•
The destruction of erythrocytes as well
as other tissue cells.
The initiation of inflammatory changes.
The lysis of bacteria cells.
Enhancement of phagocytosis
involving some opsonized particles.
Two ways of Complement’s
activation
Classical
pathway
Alternative
pathway
Damage of
membrane
Kinin activation
С1
Increasing
of permeability
of vessels
Cell
membrane
С4
Virus
neutralization
С2
С3
Phagocytosis
Virus neutralization
Immune
adherence
С5-С9
Producing of MAC
Complement Fixation
• Methodology
– Ag mixed with test serum to be assayed for Ab
– Standard amount of complement is added
– Erythrocytes coated with Abs is added
– Amount of erythrocyte lysis is determined
No Ag
Ag
Ag
Patient’s
serum
Ag