activity markers, activation pathways, antimicrobial mechanisms of macrophages.

1. Activation markers, Activation
pathways ,Antimicrobial
mechanisms of Macrophages
Dr.N.N.Jyothi
Junior resident

2. 1. Introduction
2. Macrophage activation pathways
3. Antimicrobial mechanisms of Macrophages

3. Definition:
• Macrophages are tissue cells derived from
1. BONE MARROW  HEMATOPOIETIC STEM CELL
2. YOLK SAC
3. FETAL LIVER ( devolpmental stages)
• The halflife of blood monocytes is about 1 day
tissue macrophages is several months or years,

5. Specific location Type
Circulation Monocytes
Liver Kupffer cells
Spleen, Lymph nodes Sinus histiocytes
CNS Microglia
Lungs Alveolar macrophages
Skin Langerhans
cells/dendritic cells

6. Kupffer cells
NORMAL MALARIA

7. MICROGLIA

8. HISTIOCYTES
REACTIVE HYPERPLASIA SINUS HISTIOCYTES

9. EMPERIPOLESIS KIKUCHI-FUJIMOTO

10. Alveolar macrophages
• Macrophage found in the pulmonary alveolus, near
the pneumocytes, but separated from the wall.

11. FUNCTIONS OF MACROPHAGES
1. Ingest and eliminate microbes and dead
tissues.(phagocytosis)
2. Initiate the process of tissue repair.
3. Secrete mediators of inflammation, central to
the initiation and propagation of
inflammatory reactions.
4. Macrophage-lymphocyte interactions

12. Activation pathways

14. Classic activation
1. Exposure to IFN-G, TLR
agonist (microbial
products)
2. Activation of
macrophages
3. Expression of MHC,
CD80/86.
4. APCs

15. IFN-G
• Induces production of iNOS, ROS, proteolytic
enzymes.
• Phagosome maturation.

17. Alternative activation
1. T cell  Th2 phenotype
2. Production of IL-4 & IL-13.
3. Cytokines alternatively
activate macrophages
&enhance endocytosis,
4. Increased MHC classII
expression.
5. The production of arginase
may compete for substrate
with iNOS.
6. Reduces the capacity of
these cells to kill
intracellular pathogens

18. • Promote healing of inflammatory reactions,
and the induction of humoral responses.
Fibrogenic cytokines
Angiogenesis
Remodelling collagenesis….

19. Phagocytosis
• Capability of ingesting and destroying invading
organisms.(intracellularly)
1. Recognition and attachment of the particle to
be ingested by the leukocyte.
2. Engulfment phagocytic vacuole.
3. Killing or degradation of the ingested material.

20. Recognition and attachment
1. Pathogen associated molecules PAM (such
as surface carbohydrates, peptidoglycans or
lipoproteins)
2. Pattern recognition receptors PRR, ex:-TLR
3. Opsonins

21. Opsonization
• The process in which certain antibodies
(IgGantibodies &C3b ) in the blood (known
as opsonins) bind to the surface of an invading
microorganism, which renders it more
susceptible to phagocytosis

22. • Opsonins recognized by phagocytic receptors, such
as Fcγ receptors (FcγRs) and complement receptor
3 (CR3).
• BRUTON’S DISEASE: X-linked agammaglobulinemia
(XLA)
1. Defect in the maturation of B-cells
2. Absence of immunoglobulins (Ig)
3. Defective opsonization

24. Recognition:
• Phagocyte receptors:
1. Fc mediated receptors
2. Complement mediated Receptors
3. Mannose receptors
4. Scavenger receptors
• Induce rearrangements in the actin cytoskeleton
that lead to the internalization of the particle

25. Fc Receptor-Mediated Phagocytosis
Clustering of receptors on the
surface of membrane
Phosphorylation of ITAMs ( SRC
kinase)
Activation tyrosine kinase SYK
Engulfment

26. Fc Receptor-Mediated Phagocytosis

27. Complement Receptor-Mediated
Phagocytosis
• CR1, CR3, and CR4 are expressed on
macrophages.
• Particle ingestion by CRs can be induced by
PKC activators
1. PMA,
2. TNF-α,
3. (GM-CSF).

28. Differences:
• Pseudopodia protrude from the macrophage
surface to engulf the IgG-opsonized particle,
• complement-coated particle sinks directly
into the cell.
• FcR(ROS,AAM) pro-inflammatory molecules

29. Mannose Receptor-Mediated
Phagocytosis
• Recognizes mannose & fucose on the surfaces
of pathogens and mediates phagocytosis of
the organisms
• Pro-inflammatory process
• IL-1β, IL-6, GM-CSF, TNF-α & IL-12

30. SCAVENGER RECEPTORS
• Wide variety of microbes.
• Modified LDL particles.
• The Kupffer cells in the liver are particularly
rich in scavenger receptors.
• Atherosclerosis endocytose the modified
Lipoproteins (FOAM CELL)

31. PHAGOLYSOSOME

32. • Effective phagocytosis therefore requires two
components:
1. Particle internalization.
2. Phagosomal maturation

33. ENGULFMENT
• The plasma membrane pinches off to form a
vesicle (phagosome) that encloses the
particle.
• The phagosome then fuses with a lysosomal
granule, resulting in discharge of the granule’s
contents into the phagolysosome

34. Phagosomal maturation
Early
• Refractory to fuse with lysosome
• Mildly acidic pH(6.1-6.5)
• Poor hydrolytic activity
Late
• More acidic pH((5.5–6.0)
• proteases and lysosomal-associated membrane proteins (lAMPs)
Phagolysosome.
• More acidic pH

35. Microbicidal activity of the
phagosome
1. Acidification of phagosome (V-ATPases)
2. ROS & (NO),
3. Lysosomal enzymes (antimicrobial proteins &
peptides)
• Respiratory burst is the rapid release
of reactive oxygen species (superoxide
radical and hydrogen peroxide).

37. ROS
• O2 REACTIVE OXYGEN SPECIES
• H2O2OCl2- (Myelo Peroxidase Enzyme).
• H2O2-MPO-halide system is an effective
bactericidal system.

38. • MPO deficiency increased susceptibility to infection.
• Hereditary MPO deficiency  autosomal recessive
pattern.
• acquired myeloperoxidase deficiency.
1. Pregnancy
2. Lead intoxication - Inhibits heme synthesis (a
component of mature MPO)
3. Iron deficiency
4. Severe infection - Secondary to PMN activation and
"consumption" of MPO
5. Thrombotic diseases
6. Renal transplantation
7. Diabetes mellitus
8. Hematological disorders

39. NITRIC OXIDE
• Arginine------------NO
• Enos/Nnos/Inos
• iNOS, the type that is involved in microbial
killing.
NOS

40. Role in tuberculosis

41. TH1 response
• After 3 weeks of infection
• Mycobacterial antigens displayed to T-cells by
APC.
• TH1 differentiation (IL-12)
• TUBERCULIN POSITIVITY.

42. TH1 mediated macrophage actiation
• TH1 IFN-g macrophage activation
• TNF release monocyte recruitment
• Ex: TNF antagonist (RA)  increased of TB
reactivation.

44. M.tuberculosis
• Arrest in phagosome
maturation

45. L.pneumophilia
• Failure to form
phagolysosome
• Promotes fusion with
ER-derived vesicles.

46. L.monocytogenes
• Secretes ListeriolysinO
(LLO)
• Escapes the phagosome

47. C.burnetii
• Delays phagosome
maturation
• Undergoes replication
in it.

48. Leukocyte-Mediated Tissue Injury
1. Normal defense reaction against infectious
microbes, when adjacent tissues suffer
collateral damage.
2. Inappropriately directed inflammatory
response against host tissues autoimmune
diseases.
3. Host reacts excessively  as in allergic
diseases (asthma).

49. Phagocyte defects
1. Chronic granulomatous disease of childhood
(CGD),
2. Chediak-Higashi syndrome (CHS),
3. Hyper immunoglobulin-E -recurrent infection
(Job's) syndrome (HIE).
4. Myeloperoxidase (MPO) deficiency.

50. Phagocyte defect inheritence defect
1 Chronic
granulomatous
disease (PIDD)
X-
linked/Autosomal
recessive
Hydrogen
peroxide
2 Chediak higashi
syndrome LYST
GENE MUTATION
Autosomal
recessive
LYST gene
mutation
Non functional
lysosomes
3 Job's syndrome
(HIE). STAT3 GENE
MUTATION
Autosomal
dominant or
autosomal
recessive.
High
concentrations
of the serum
IgE.
4 MPO DEFICIENCY Hereditary/acquir
ed
Mpo deficiency

51. 1. CGD  defective oxidative metabolism
involved in killing catalase-positive organisms.
2. CHS  giant granules defective in fusing with
phagosomes and subsequent killing of ingested
organisms.
3. HIE abnormal chemotaxis and elevated IgE
levels and are susceptible to skin infections with
Staphylococcus aureus and recurrent
sinopulmonary infections.

52. 4. MPO-deficiency go undetected since they
rarely have recurrent infections unless they have
a concomitant disease such as diabetes mellitus.

53. Macrophage-Lymphocyte interaction

55. References
• Kumar, V., Abbas, A. K., Fausto, N., Robbins, S. L., & Cotran, R. S. Robbins and
Cotran pathologic basis of disease. Philadelphia: Elsevier Saunders. Inflammation
& repair pg no 88-104.
• White CJ, Gallin JI. Phagocyte defects. Clin Immunol Immunopathol. 1986;40:50–
61
• Aderem A, Underhill DM. Mechanisms of phagocytosis in macrophages. Annual
Review of Immunology. 1999;17:593–623.
• de Villiers WJ, Smart EJ. Macrophage scavenger receptors and foam cell
formation. J Leukoc Biol. 1999;66:740–6
• Gordon, Siamon & O Martinez, Fernando. (2010). Alternative Activation of
Macrophages: Mechanism and Functions. Immunity. 32. 593-604.
• R.S. Flannagan, G. Cosío, S. Grinstein Antimicrobial mechanisms of phagocytes and
bacterial evasion strategies Nat. Rev. Microbiol., 7 (2009), pp. 355-366