1. Inflammation
Dr (Prof) Vishal Saxena
MBBS, MD(Path)

3. Inflammation
Response of the vascularized living tissue to injurious agents and necrotic cells, leading to accumulation of fluid and leukocytes in extra-vascular tissue.
Injurious agents/harmful stimuli:
Microbial pathogen
Chemical or
Physical agents etc.

4. What are the symptoms of fire ant bite? A. Pain B. Redness
C. Rise of temperature
D. Swelling
E. All of above

5. Objectives of today’s lecture
Acute Inflammation
definition, purpose, 5 cardinal signs
vascular events, cellular events.
Chemical mediators of acute inflammation
Outcomes of acute inflammation
Different types of acute inflammation

6. Inflammation
Purpose:
To defend against and to eliminate the injurious agent responsible for injury.
Clear the tissue of the necrotic material (consequences of injury) and
To initiate healing and repair of injured tissue.

7. The suffix which indicates inflammation is "-itis"
Examples:
Appendix  appendicitis
Pancreas  pancreatitis
Meninges  meningitis
Pericardium  pericarditis
Liver  hepatitis
Joints  Arthritis

8. Patterns of inflammation
Acute: characteristics
Early response to injury (infection, chemical agents etc)
Rapid in onset
Short duration (minutes – days)
Fluid and plasma protein exudation (edema)
Accumulation of Neutrophils.
2. Chronic: characteristics
Longer duration (days – years)
Influx of lymphocytes & macrophages.

9. Terms for abnormal accumulations of fluid
Exudation
Exudate
Transudate
Edema
Pus

11. Edema: excess amount of fluid in the interstitial tissue spaces or body cavities.
Can be exudate or transudate 2. Exudate: an inflammatory extravascular fluid with a high protein concentration, > cells/ cell debris & a specific gravity > 1.020
implies: significant alteration in permeability of small blood vessels in an area of injury.
Functions of exudate:
Supply neutrophils
Localize infection (fibrin)
Dilute the toxin
Provide nutrition to cells
Supply antibodies

12. Exudate : microscopy
Neutrophils
Exudate rich in fibrin

13. 3. Transudate: an extravascular fluid with a low protein content, few or no cells & Sp.Gr < 1.012
Results due to increased hydrostatic pressure.
4. Exudation: the escape of fluid, proteins & blood cells from the vascular system into the interstitial tissue or body cavities.
5. Pus (purulent exudate) is inflammatory
exudate rich in neutrophils and debris of
necrotic cells.

14. Pitting Edema Laryngeal edema A B
A: Here is simple edema, or fluid collection within tissues.
This is "pitting" edema because, on physical examination, you can press your finger into the skin and soft tissue and leave a depression.
B:This example of edema with inflammation is not trivial at all: there is marked laryngeal edema such that the airway is narrowed.
This is life-threatening. Thus, fluid collections can be serious depending upon their location. A B

15. Pleural effusion
Here is an example of fluid collection into a body cavity, or an effusion.
This is a right pleural effusion (in a baby). Note the clear, pale yellow appearance of the fluid. This is a serous effusion.
Extravascular fluid collections can be classified as follows:
Exudate: extravascular fluid collection that is rich in protein and/or cells. Fluid appears grossly cloudy.
Transudate: extravascular fluid collection that is basically an ultrafiltrate of plasma with little protein and few or no cells.
Fluid appears grossly clear.

16. Skin abscess A B A: Abscess: localized collection of pus.
B: Microscopically,the abscess shows an extensive neutrophilic exudate (pus). B

17. Hallmark of acute inflammation
Vasodilatation
Increased vascular permeability
Exudate formation and
Entry of neutrophils to the site of injury.
These events are modulated by release of chemical mediators.

18. Which of the following can cause inflammation ? A. Infection
B. Thorn prick
C. Acid exposure
D. All of above

19. Stimuli for acute inflammation
Acute inflammation triggered by a variety of stimuli:
Infections: bacterial, viral, parasitic.
Trauma: blunt and penetrating.
Physical and chemical agents: thermal injuries, irradiation, chemicals etc.
Tissue necrosis.
Foreign bodies: splinter, dirt, suture.
Immune reactions : (hypersensitivity reactions).
All of these induce acute inflammatory reaction with some distinct features.
But all acute inflammatory responses have the same basic features.

20. Signs of acute inflammation

21. The 5 Cardinal Signs of Acute
Heat Redness Swelling Pain Loss Of
Func.

22. Local signs of acute inflammation: Mechanism
Calor = Heat
Histamine dependent vasodilatation.
Rubor = Redness
Tumor = Swelling
Histamine dependent increase in vascular permeability.
Dolor = Pain
Due to prostaglandin E2 and bradykinin.
Functio Laesa = loss of function
Sum total of the effects of inflammation.

23. Let’s Study Acute Inflammation
Important components of acute inflammation:
Vascular events
Cellular events
Chemical mediators

24. Which of the following cells secrete histamine?
Neutrophil
Macrophage
Endothelial cell
Mast cell
Neuron

25. Vascular events Vasodilatation of arterioles:
Mast cells release histamine which acts on vascular smooth muscle cells causing
Increased blood flow (hyperemia) and hydrostatic pressure.
Produces redness and heat.

26. Vascular events 2.Increased permeability of venules:
Histamine contracts endothelial cells.
Causing movement of fluid into interstitial tissue.
3.Slowing of blood flow (stasis):
Caused by outflow of fluid from blood vessels  increased viscosity.
Rouleaux formation (stack of coins)
Alteration in laminar flow
Neutrophil margination

27. Mechanism of increased vascular permeability

28. Immediate transient response Immediate sustained response1
Immediate transient
response 2
1. Gaps due to endothelial contraction
Occurs immediately after exposure to mediator and is short lived , hence known as “immediate transient response”
2. Direct endothelial injury
Due to direct effect of injurious agent on endothelial cell  delayed endothelial damage.
Affects Arterioles, capillaries and venules.
Cause: Toxins, burns, chemicals.
Fast and may be long lived.
Immediate sustained
response

29. Delayed prolonged leakage Lasts for hours to days X ray, sunburn
? Apoptosis of endothelial cells 3 4
3. Delayed prolonged leakage
Leakage begins after a delay of 2-12 hours and lasts for hours to days.
Seen in: Injury caused by exposure to radiation, sunburn etc.
Mechanism: ? Apoptosis of endothelial cells.
4. Leukocyte dependent injury
Leukocytes adhere to endothelium and release FR & proteolytic enzymes  endothelial injury and detachment
Mostly venules
Pulmonary capillaries (Importance?) (answer: ARDS)

30. 5. New blood vessel formation
Occurs at sites of angiogenesis.
New blood vessels are leaky as they have endothelial gaps.

31. Mechanism of increased vascular permeability.
SUMMARY
Gaps due to Endothelial cell contraction.
Direct endothelial injury resulting in endothelial cell necrosis and detachment.
Delayed prolonged leakage.
Leukocyte mediated endothelial injury.
Leakage from new blood vessels.
Transcytosis [cell channels].
*Increased vascular permeability is a hallmark of acute inflammation.

32. Leukocyte extravasation and Phagocytosis
Cellular events
Leukocyte extravasation and
Phagocytosis

33. Sequence of events in the extravasation of leukocytes
Margination
Rolling
Adhesion
Transmigration (also called diapedesis)
Migration toward chemotactic factor = chemotaxis

36. Margination Accumulation of leukocytes along the endothelial surface:
Partly mechanical and
Partly mediated by chemical mediators
C5a, leukotrine B4 and bacterial products.

37. Rolling, adhesion and transmigration
Mediated by binding of complementary adhesion molecules on leukocytes and endothelial surfaces

38. Mucin like glycoproteins
Selectins
Integrins
Adhesion molecules
Immunoglobulins
Adhesion molecules play an important role in acute inflammation
Are divided in to four families:
selectins
integrins
immunoglobulin-family adhesion proteins
mucin like glycoproteins.
Mucin
like
glycoproteins

39. Selectins cause weak binding and play a role in rolling.
Integrins cause firm binding and play a role in firm adhesion of neutrophils to endothelial surface.

40. At what stages do they function?
Selectins are involved in weak binding and rolling.
Integrins are involved in firm adhesion and transendothelial migration.
PECAM-1, another adhesion molecule expressed on both leukocytes and endothelial cells, is involved in transmigration.

41. Rolling
E-selectins and P-selectins present on endothelial cell surface.
Bind to sialyl-lewis X on leukocytes.
The binding mediated by selectins is weak.
Selectins are present at very low levels in normal endothelium.
During inflammation they increase in number after stimulation by specific mediator (histamine, thrombin)
P-selectin: stored in endothelial Weibel Palade bodies.

42. Redistribution of P- Selectin
P-Selectin-normally present in the Weibel-Palade bodies of endothelial cells.
Redistributed to the cell surface:
Histamine
Thrombin

43. Adhesion
Cytokines (TNF and IL-1) increase expression of endothelial adhesion molecules (ICAM-1 and VCAM-1 ).
Leukocytes are activated by chemicals (C5a and LTB4) to increase binding affinity of integrins.
Integrins bind to ICAM-1 and VCAM-1 on endothelial surface.
This binding is stable and firm.
Note: types of integrins
VLA-4 beta 1 integrin
LFA-1 beta 2 integrin
Mac-1 beta 2 integrin
INTEGRINS
Cause stable binding and adhesion.
Present on the surface of leukocytes.
VLA-4 beta 1 integrin
LFA-1 beta 2 integrin
Mac-1 beta 2 integrin
Integrins interact with integrin receptors on endothelial cells
ICAM-1
VCAM-1
Integrins- normally present on leukocyte surface, but do not bind to their ligands unless activated by chemical mediators (C5a)

44. Transmigration Leukocytes emigration  pseudopods.
Interaction of platelet endothelial cell adhesion molecule 1 (PECAM-1) on leukocytes and endothelial cells mediates transmigration between cells.
Neutrophils release type IV collagenase that degrades the Basement membrane.
Fluid rich in protein and neutrophils then accumulates in the interstitial tissue. The fluid is called EXUDATE.

45. Transmigration

46. Endothelial and leukocyte adhesion molecule pairs
Endothelial molecule
Leukocyte molecule
Role
P-selectin
Sialyl-Lewis X
Rolling
E-selectin
Sialyl-Lewis X
Rolling
GlyCam-1/CD34
L-Selectin
Rolling
VCAM-1
VLA-4 integrin
Adhesion
ICAM-1
LFA-1 & MAC-1 integrins
Adhesion
PECAM-1
PECAM-1
transmigration

47. Why learn these adhesion molecules??
Adhesion molecule deficiency associated with increased susceptibility to develop recurrent bacterial infections.
Examples of adhesion molecule deficiencies include:
LAD -1 (leukocyte adhesion deficiency type 1)
LAD-2 (leukocyte adhesion deficiency type 2)

48. Chemotaxis
Chemotaxis is the attraction of cells toward a chemical mediator that is released in the area of inflammation.
Important chemotactic factors for neutrophils:
Exogenous:
Bacterial products, such as N-formyl-methionine
Endogenous:
Leukotrine B4 (LT-B4)
Complement system products (C5a)
Alpha Chemokines (IL-8)
*Chediak Higashi syndrome and DM have defective Chemotaxis  prone to infections.
How do we measure potency of chemotactic agent: Boyden chamber technique (2 chambers with mesh filters- measures how good a chemotactic agent is).

49. Which of the following cells can perform phagocytosis?
A. Neuron
B. Muscle cell
C. Endothelial cell
D. Macrophage
E. Red blood cell

50. Phagocytosis
Engulfment of particulate material (e.g. tissue debris, living and dead bacteria, other foreign particles) by phagocytic cells.
Neutrophils and macrophages the most important Phagocytic cells.
Phagocytosis: Three steps
Recognition and attachment
Engulfment
Killing and degradation of the ingested material

51. Recognition and attachment
Receptors on leukocytes recognize the particle to be ingested.
Opsonization: facilitates phagocytosis
Is coating of particulate matter by substances referred to as OPSONINS.
Important opsonins
IgG
Complement system product C3b
Plasma protein – Collectins
Opsonization is defective in Bruton’s agammaglobulinemia (due to decreased levels of IgG).

52. Engulfment
Triggered by binding of opsonised particle to phagocytic receptor.
Neutrophil sends out cytoplasmic processes that surround the bacteria.
The bacteria are internalized within a phagosome
The phagosome fuses with lysosome to form phagolysosome.
Release of lysosomal contents (degranulation).

53. Phagocytosis

54. Intracellular microbial killing
The final step in Phagocytosis of microbes is killing and degradation.
Mediated within phagocytic cells by:
Oxygen dependent and
Oxygen independent mechanisms

55. Oxygen dependent killing (H2O2-MPO-halide system)
The most efficient bactericidal system in neutrophils.
Killing of bacteria:
by reactive oxygen species and
hypochlorous acid.
After Phagocytosis has occurred, NADPH oxidase (located in the membrane of neutrophils and monocytes) converts molecular oxygen into superoxide free radical in presence of NADPH.
Energy given off in this reaction is called respiratory burst.
NADPH oxidase: enzyme located in the membrane of neutrophils and monocytes.
The H2O2-MPO-halide system the most efficient bactericidal system in neutrophils.

56. 2O2 + NADPH 2O2 -. + NADP+ + H+ 2O2 -. + H+ H2O2 HOCl. H2O2 + Cl-
oxidase
Superoxide anion
2O2 -. + H+
H2O2
SOD
Hydrogen peroxide
HOCl.
H2O2 +
Cl-
Myeloperoxidase
MPO
Hypochlorous
acid

57. Hypochlorous acid = bleach  destroys bacteria.
NBT (nitroblue tetrazolium test) dye test : evaluates the integrity of the respiratory burst.
Neutrophils convert a colorless dye into a colored dye if respiratory burst system is intact.
Chronic granulomatous disease of childhood:
absent NADPH oxidase-
absent respiratory burst;
negative NBT dye test.

58. Oxygen independent killing
Less effective than oxygen dependent killing
Mediated by substances in leukocyte granules:
Lysozyme
Lactoferrin
Major basic proteins
Bacterial permeability increasing protein (BPI)
Defensins

59. Degradation The dead organism: degraded by lysosomal acid hydrolases.
Thank You !