Macrophages

activity markers, activation pathways, antimicrobial mechanisms of macrophages.

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

2. Introduction Macrophage activation pathways Antimicrobial mechanisms of Macrophages

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

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

5. Kupffer cells NORMAL MALARIA

6. MICROGLIA

7. HISTIOCYTES REACTIVE HYPERPLASIA SINUS HISTIOCYTES

8. EMPERIPOLESIS KIKUCHI-FUJIMOTO

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

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

11. Activation pathways

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

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

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

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

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

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

18. 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

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

20. Recognition : Phagocyte receptors : Fc mediated receptors Complement mediated Receptors Mannose receptors Scavenger receptors Induce rearrangements in the actin cytoskeleton that lead to the internalization of the particle

21. Fc Receptor-Mediated Phagocytosis

22. Fc Receptor-Mediated Phagocytosis

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

24. 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

25. 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

26. 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)

27. PHAGOLYSOSOME

28. Effective phagocytosis therefore requires two components: Particle internalization. Phagosomal maturation

29. 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

30. P hagosomal maturation

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

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

33. MPO deficiency  increased susceptibility to infection. Hereditary MPO deficiency  autosomal recessive pattern. acquired myeloperoxidase deficiency. Pregnancy Lead intoxication  - Inhibits heme synthesis (a component of mature MPO) Iron deficiency Severe infection - Secondary to PMN activation and "consumption" of MPO Thrombotic diseases Renal transplantation Diabetes mellitus Hematological disorders

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

35. Role in tuberculosis

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

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

38. M.tuberculosis Arrest in phagosome maturation

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

40. L.monocytogenes Secretes ListeriolysinO (LLO) Escapes the phagosome

41. C.burnetii Delays phagosome maturation Undergoes replication in it.

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

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

44. 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/acquired Mpo deficiency

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

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

47. Macrophage-Lymphocyte interaction

48. 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