Immunity

1. IMMUNITY
DR. JUNEEM K M
DEPARTMENT OF ORAL PATHOLOGY

2. CONTENTS
• INTRODUCTION
• TYPES OF IMMUNITY
• INNATE IMMUNITY

3. IMMUNITY :
• Immunity is derived from the latin word
“immunis” meaning to be exempted from
• Its the ability of an organism to resist a
particular infection or toxin by the action of
specific antibodies or sensitized white blood
cells.
• The immune system is a system of biological
structures and processes within an organism
that protects against disease

4. • The Boy in the Plastic Bubble
is a 1976 made-for-TV movie
inspired by the lives of David
Vetter and Ted DeVita, who
lacked effective immune
systems.

6. Invading
microbes
(pathogens)
External defenses
Skin
Mucous membranes
Secretions
INNATE IMMUNITY
Rapid responses to a
broad range of microbes
ACQUIRED IMMUNITY
Slower responses to
specific microbes
Internal defenses
Phagocytic cells
Inflammatory response
Humoral response
(antibodies)Antimicrobial proteins
Natural killer cells Cell-mediated response
(cytotoxic
lymphocytes)

7. Immunity: Two Intrinsic Defense
Systems
INNATE (NONSPECIFIC)
SYSTEM
• responds quickly
• no need to decipher pathogen’s
identiy
• Always present in the body

8. • consists of:
▫ First line of defense – intact skin and
mucosae prevent entry of microorganisms
• Physical barriers
- skin
- mucus membrane
- mucus
- hair
- stream of tears
- urine
- defecation
• Chemical barriers
– pH (skin ,stomach, vagina)
– sebum
– enzymes (stomach, tears)

9. Second line of defense –
1. Phagocytes
2. natural killer (NK) cells
3. Inflammatory response enlists macrophages,
mast cells, WBCs, and chemicals
4. Antimicrobial proteins in blood and tissue
fluid

10. 1. Phagocytes
• Macrophages are the chief phagocytic cells
• Free macrophages wander throughout a region in
search of cellular debris
• Kupffer cells (liver) and microglia (brain) are fixed
macrophages
• Neutrophils become phagocytic when encountering
infectious material
• Eosinophils are weakly phagocytic against parasitic
worms
• Mast cells bind and ingest a wide range of bacteria

11. Phagocytic Mobilization
• Occurs in four main phases:
LEUKOCYTOSIS
MARGINATION
DIAPEDESIS
CHEMOTAXIS

13. Inflammatory Response: Phagocytic Mobilization
Neutrophils
enter blood
from bone
marrow
1
2
3
4
Margination
Diapedesis
Positive
chemotaxis
Capillary wall
Endothelium
Basal lamina
Inflammatory
chemicals
diffusing from
the inflamed
site act as
chemotactic
agents
3

14. MECHANISM OF PHAGOCYTOSIS

15. 2.Defense by NK cells
• NK cells or natural killer cells
• Have ability to kill a wide variety of
microorganisms and tumour cells
• Unlike B and T cells they lack specific surface
antigen receptors.
• Present in spleen, lymph nodes , bone marrow
and blood

16. • They kill microbes by the following mechansims:
1. Osmotic lysis by incorporating perforins into
the surface of the microbes
2. Release interferons that activate phagocytosis
and immunity

17. 3. Inflammation: Tissue Response to
Injury• The inflammatory response is triggered
whenever body tissues are injured
▫ Prevents the spread of damaging agents to
nearby tissues
▫ Disposes of cell debris and pathogens
▫ Sets the stage for repair processes

18. • The four cardinal signs of acute
inflammation are
1. redness ( RUBOR)
2. heat (CALOR)
3. swelling (TUMOR)
4. pain (DOLOR)
5. Functiolesia

19. 3 stages of inflammation
• 1. VASODILATION AND INCREASED
PERMEABILITY
• 2. PHAGOCYTE MIGRATION AND
PHAGOCYTOSIS
• 3. TISSUE REPAIR

20. • Major events in the local inflammatory response
Figure 43.6
Pathogen Pin
Macrophage
Chemical signals
Capillary
Phagocytic cells
Red blood cell
Blood
clotting
elements
Blood clot
Phagocytosis
Fluid, antimicrobial proteins,
and clotting elements move
from the blood to the site.
Clotting begins.
2Chemical signals released
by activated macrophages
and mast cells at the injury
site cause nearby capillaries
to widen and become more
permeable.
1 Chemokines released by various
kinds of cells attract more
phagocytic cells from the blood
to the injury site.
3 Neutrophils and macrophages
phagocytose pathogens and
cell debris at the site, and the
tissue heals.
4

22. 4. Antimicrobial Proteins
• Enhance the innate defenses by:
Attacking microorganisms directly
Hindering microorganisms’ ability to reproduce
• The most important antimicrobial proteins are:
▫ Interferon
▫ Complement proteins

23. 4 a. Interferon (IFN)
• Genes that synthesize IFN are activated when a
host cell is invaded by a virus
• Interferon molecules leave the infected cell and
enter neighboring cells
Interferon stimulates the neighboring cells to
activate genes for PKR (an antiviral protein)
PKR nonspecifically blocks viral reproduction in the
neighboring cell

24. Interferon Family
• Interferons are a family of related proteins
each with slightly different physiological
effects
• Lymphocytes secrete gamma () interferon,
but most other WBCs secrete alpha ()
interferon
• Fibroblasts secrete beta () interferon
• Interferons also activate macrophages and
mobilize NKs

25. 4 b. Complement
• 20 or so proteins that circulate in the blood in an
inactive form
• Proteins include C1 through C9, factors B, D,
and P, and regulatory proteins
• Provides a major mechanism for destroying
foreign substances in the body

26. Complement Pathways
• Complement can be activated by two pathways:
classical and alternative
• Each pathway involves a cascade in which
complement proteins are activated in an orderly
sequence and where each step catalyzes the next

27. Complement Pathways

28. REFERENCE:
1. Guyton And Hall Textbook Of Medical
Physiology, 12th Edition
2. Textbook Of Medical Physiology , 2nd Edition,
Prof. GK Pal
3. Textbook Of Microbiology, 8th Edition;
Ananthnarayan And Paniker
4. Essential Pathology For Dental Students , 3rd
Edition; Harsh Mohan