The document discusses the innate immune system and its mechanisms for defending against pathogens. It describes the skin and mucous membranes as the first line of defense through physical and chemical barriers. The second line of defense includes inflammatory responses, fever, phagocytic cells, and antimicrobial substances that work in a nonspecific manner. Key components that provide innate immunity are natural barriers, defensive cells, inflammation, fever, and the complement system.

2. THE CONCEPT OF IMMUNITY
 Immunity
• Ability to ward off disease caused
by microbes
 Susceptibility
• Vulnerability or lack of immunity
 Innate
• Defenses present at birth
 Specific resistance
• Immunity/resistance to a specific
pathogen
 Nonspecific resistance
• Defenses against any pathogen

4. Skin
Mucous membranes
Ciliary escalator
Lacrimal apparatus
Saliva
Urine
Vaginal secretions
MECHANICAL FACTORS

5. Skin

6. Skin
• Intact skin prevents microbes from
entering the skin
• Broken skin – port of entry for microbes
• How?
– Bacteriocidal secretion by the sebaceous
glands
– Keratin - Desquamation
– Dryness - Perspiration

7. Mucous Membranes
• Barrier protection
• Lining of the respiratory tract, GI tract and
genitourinary tract
• Mucus – a glycoprotein produced by
goblet cells that keeps surfaces moist
• Mucosal cells are rapidly dividing  flush
out of the body along with attached
bacteria

8. Epithelial lining of the trachea

9. • Digestive tract
–Mouth and lower digestive tract
–How?
• Mucus
• Saliva (contains lysozyme)
• Bile (alkaline) in small intestine
• Stomach acids
• Defecation
• Mucus contain antibacterial agents,
antibodies and immune cells called
phagocytes
Mucous Membranes

10. • Genitourinary tract
–Urinary tract is sterile in a health person
except the distal urethra
–How?
• Urination
• Secretion (vaginal and seminal fluid)
• Low pH of vagina (presence of
several Lactobacillus sp.)
Mucous Membranes

11. • Respiratory tract
– Nose - nasal hair, mucus
secretions (phagocytes
and antibacterial
enzymes), irregular
chambers
– ciliated epithelium (nasal
cavity, sinuses, bronchi
and trachea)
– Cough reflexes
– Alveolar macrophages
Mucous Membranes

12. Lacrimal apparatus
• Protection for the eye
• Tears are produced by the lacrimal gland
• Tears and their washing action helps keep
the surface of the eye free from bacterial
accumulation
• LYSOZYME is also found in tears and this
enzyme has anti-bacterial action as well

13. Lacrimal apparatus

14. CHEMICAL FACTORS
 Sebum
 Perspiration – lysozyme
 Gastric juice
 Vaginal secretions – glycogen
 Urine – lysozyme, pH (average of
6), urea and other metabolic
products

15. NORMAL MICROBIOTA
 Microbial antagosism
• Normal microbiota compete
with pathogens

16. SECOND LINE of DEFENSE
• Once beyond the protective
outer barrier of the body, the
invading microbes will encounter
a series of nonspecific cellular
and chemical defense
mechanisms

17. Mechanisms:
Inflammation – a series of events that
removes or contain the offending agent
and repair the damage
Chemotaxis – movement of cells toward
a chemical influence (chemokines or
chemotatic agents)
Phagocytosis – process in which cell
ingest foreign matter
Many are carried out by the white blood
cells in blood

18. Blood Components
• Fluid portion
–Serum: liquid portion of clotted blood
–Plasma: liquid portion with clotting factors
–“Plasma can clot; Serum cannot”
–Contains antibodies & other proteins
• Clotting factors (proteins)
–Fibrinogen
–Prothrombin

19. I. Erythrocytes – red blood cells
(RBC) – carry oxygen and carbon
dioxide; no nucleus
II. Leukocytes – white blood cells
(WBC) - defense
III. Platelets – thrombocyte
particles – clotting; no nucleus
 Formed Elements in Blood

20.  White Blood Cells
• Granulocytes
–Neutrophils
–Eosinophils
–Basophils
• Agranulocytes
–Monocytes
–Dendritic cells
–Lymphocytes

21. Monocytes
(marcophage)
Lymphocytes
Neutrophils
Eosinophils
Basophils
Erthrocytes
(RBC)
Platelets
Wright’s stain of the peripheral blood cells can identify
granulocytes based on properties of the granules. It contain
two dyes:
• Eosin dye stains basic cell components  reddish
• Methylene blue dye stain acidic cell components  blue-ish
 White Blood Cells

22. WBC differentials
• Never – neutrophils 60-70%
• Let – lymphocytes 20-25%
• Monkeys – monocytes 3-8%
• Eat – eosinophils 2-4%
• Bananas - basophils 0.5-1%

23. Formed Elements In Blood

24. Formed Elements In Blood
Wandering or Fixed

25. Can you identify these leukocytes?
erythrocyte
platelet
A
B
C
D
E
F
G
H
I

26. Granulocytes
 Neutrophils (aka polymorphonuclear cells or
PMN)
• Most common leukocytes in the blood.
Granules unstained.
• mobile cells and can pass through
capillaries and engulf bacteria by
phagocytosis
• secrete a fever inducing agent called
pyrogen which also helps the body
fight infection.
 Eosinophils
• the granules of cytoplasm are stainable
with eosin (red)
• The exact function of eosinophils has
been a mystery for many years, but
research has pointed to its role in
allergy, asthma and parasitic
(helminth) infection; some
phagocytosis.

27.  Basophils
•rarest WBC in normal
blood
•Blue granules contain
histamine
•play a role in immediate
hypersensitivity reactions
and in some cell-mediated
delayed reactions, such as
contact hypersensitivity in
humans, skin graft or
tumor rejections
Granulocytes

28. Monocyte (Macrophage)
 Monocytes (the blood form)
• the largest WBC's normally found in
blood
• horseshoe or "U" shape nucleus, or it
may be folded
• travel to different tissue to mature into
specific macrophage
 Macrophage
• As it developed from monocytes, its
size can increase 2-3 times
• Wandering – motile and travel in
bloodstream; found throughout body
• Fixed (histiocytes)– attached and
remain in the tissue
• Removal and engulfment of foreign
particles and useless body
cells/material

29.  Lymphocytes
• The lymphocyte nucleus is
usually round to slightly
indented with a sharply
defined edge, and deep,
dense purple. Cytoplasm
may be scant or form a
narrow rim around the
nucleus.
• Cornerstone of the
immune system: antibodies
production & cell-mediated
immunity

30.  the ingestion of microorganisms or other matter
by a cell. Many white blood cells engulf invasive
microorganisms by the process of phagocytosis.
– 1. Chemotaxis - phagocytes are attracted to
microorganisms.
– 2. Attachment - phagocyte adheres to the
microbial cell. This adherence may be
facilitated by opsonization – coating the
microbe with plasma proteins.
– 3. Ingestion - Pseudopods of phagocytes
engulf the microorganism and enclose it in a
phagosome to complete ingestion.
– 4. Digestion - Lysosomes fuse with the
phagosome to form a digestive vacuole. The
microbe is killed and digested.
Phagocytosis

31. Stages of phagocytosis

32. Phagocytosis

33. Inflammation
• Four cardinal signs
– Redness
– Heat
– Swelling
– Pain
• Primary functions
– Localize infection
– Neutralize toxins at
injury site
– Repair damage
tissue
• Major events
– Vasodilation
– Increase
permeability of
capillaries
– Mobilization of
leukocytes to site
of injury
(chemotaxis &
emigration)
– Phagocytosis

34. Second Line of Defense
Inflammation

35. Inflammation – cont.
(Chemotaxis)

36. Fever
• Systemic response to injury
• Abnormally high body temperature
• Shivering - the result of a new higher set
point for body temperature
• Death results if body temperature rises
above 44 to 46 degrees Celsius

37. Antimicrobial Substances
• Complement
• Interferon
• Iron-binding proteins
• Anti-microbial peptides

38. Complement
• Defensive system of over 30 proteins that
are made in the liver and circulate in the
blood and tissues
• Activation of complement destroys
microbes by lysis, inflammation, and
phagocytosis
• Complement proteins act in a CASCADE,
that is, one reaction triggers another

39. Complement

40. Interferon
• Classes of anti-viral proteins
• First discovered in the mid 1950’s
• Produced by cells such as lymphocytes,
macrophages and fibroblasts AFTER viral
stimulation - RNA viruses
• Interfere with viral multiplication

41. Interferon
• Three classes of interferons
– Alpha - leukocytes
– Beta - fibroblasts
– Gamma - lymphocytes (T cells)
• Produced after viral infection
• Induces near by cells to produce anti-viral to
protect against the virus
• Currently produced by recombinant DNA
technology

42. Summary of Innate Immunity Defenses
FIRST LINE OF DEFENSE: SKIN AND MUCOUS MEMBRANES
Component Function
PHYSICAL FACTORS
 Epidermis of skin Forms a physical barrier to the entrance of
microbes
 Mucous membranes Inhibit the entrance of many microbes
 Mucus Traps microbes in respiratory and GI tracts
 Lacrimal apparatus Tears dilute and wash away irritating substances
and microbes
 Saliva Washes microbes from surfaces of teeth and
mucous membranes of mouth
 Hairs Filter out microbes and dust in nose
 Cilia Together with mucus, trap and remove microbes
and dust from upper respiratory tract
 Epiglottis Prevents microbes from entering lower resp. tract
 Urine Washes microbes from urethra
 Vaginal secretions Move microbes out of female reproductive tract
 Peristalsis, defecation, vomiting Expel microbes from the body

43. CHEMICAL FACTORS
Component Function
 Sebum Forms a protective acidic film over the skin surface that
inhibits growth of many microbes
 Lysozyme Enzyme that digests peptidoglycan in perspiration,
tears, saliva, nasal secretions, urine, and tissue fluids
 Saliva Contains lysozyme, and uric acid, which inhibit
microbes; and immunoglobulin A, which prevents
attachment of microbes to mucous membranes. Slight
acidity discourages microbial growth
 Gastric juice Destroys bacteria and most toxins in stomach
 Urine Contains lysozyme, urea, and uric acid, which inhibit
microbes; slight acidity discourages microbial growth
 Vaginal secretions Slight acidity discourages bacterial and fungal growth

44. SECOND LINE OF DEFENSE
Component Functions
 Defensive Cells
• Phagocytes Phagocytosis by cells such as neutrophils, eosinophils,
dendritic cells, and macrophages
• Natural killer (NK)
cells
Kill infected target cells by releasing granules that
contain perforin and granzymes. Phagocytes then kill the
infected microbes
 Inflammation Confines and destroys microbes and initiates tissue
repair
 Fever Intensifies the effects of interferons, inhibits growth of
some microbes, and speeds up body reactions that aid
repair
 Antimicrobial Substances
• Complement system Causes cytolysis of microbes, promotes phagocytosis
and contributes to inflammation
• Interferons Protect uninfected host cells from viral infection
• Iron-binding proteins Inhibit growth of certain bacteria by reducing the amount
available iron
• Antimicrobial
peptides
Inhibit cell wall synthesis, form pores in the plasma
membrane that cause lysis; and destroy DNA and RNA