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Immunity 1

Innate immunity

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Immunity 1

  1. 1. Lecture presented by – Dr.D.W.Deshkar Assistant Professor Dept.of Microbiology D.Y.Patil Medical College ,Kolhapur
  2. 2. DWD 3 Immunity  Term “immunity”(Latin word “immunita” means freedom from disease) is defined as the resistance offered by the host against microorganisms or any foreign substances. Protection against infectious diseases is only one of the consequences of Immune Response, which in its entirety is concerned with the reaction of the body against any foreign Antigen.
  3. 3. DWD 4 Immunity Immune system evolved to protect multicellular organisms from pathogens.  Highly adaptable it defends the body against diverse invaders.  The immune system generates an enormous variety of cells & molecules capable of specifically recognizing and eliminating foreign invaders, all of which act in a dynamic network.
  4. 4. DWD 5 Immunity  Protection by immune system – divided into two related activities – recognition & response.  Immune recognition is remarkable for its capacity to distinguish foreign invaders from self components.  The immune system is able to recognize molecular patterns that characterize groups of common pathogens & deal with these in a rapid & decisive manner.
  5. 5. DWD 6 Immunity  It can even detect subtle chemical differences that distinguish one foreign pathogen from another.  Immune system is able to discriminate between foreign molecules & the body’s own cells.( self – non self discrimination).  Recognition of pathogen by immune system triggers an effector response that eliminates or neutralizes the invader.
  6. 6. DWD 7 Types of Immunity Innate (Native) Immunity: 1. Non-Specific 2. Specific Species Racial Individual Species Racial Individual Acquired (Adaptive) Immunity: 1. Active 2. Passive Natural Natural Artificial Artificial
  7. 7. DWD 8
  8. 8. • Innate immunity consists of defenses against infection that are ready for immediate activation prior to attack by a pathogen. Includes physical, chemical & cellular barriers. • The less specific component of immunity – Innate immunity, provides the first line of defense against infection. • Most components of innate immunity are present before the onset of infection & constitute a set of disease resistance mechanisms that are not specific to a particular pathogen, but include cellular & molecular components that recognize classes of molecules peculiar to frequently encountered pathogens. DWD 9 Innate (Native) Immunity
  9. 9. DWD 10 Innate (Native) Immunity Resistance to infections possessed by an individual by virtue of his/her genetic & constitutional make-up. Does not depend on prior contact with mos. (infection or immunisation). Non-Specific Innate Immunity It indicates a degree of resistance to infection in general Specific Innate Immunity It indicates a degree of resistance to infection towards a particular pathogen
  10. 10. DWD 11 Innate (Native) Immunity  Innate immunity includes molecules & cellular mechanisms predeployed before an infection and poised to prevent or eliminate it.  This highly effective first line of defense prevents most infections at the outset or eliminates them within hours of encounter with the innate immune system.  The recognition elements of innate immune system precisely distinguish between self and pathogens, but they are not specialized to distinguish small differences in foreign molecules.
  11. 11. 12 Innate (Native) Immunity Non-Specific Specific Species SpeciesRacial RacialIndividual Individual
  12. 12. DWD 13 Innate (Native) Immunity Species Immunity: It refers to a total or relative response to a pathogen, shown by all members of a Species. Ex. Human Species exhibit resistance to Plant Pathogens. Racial Immunity: Difference in susceptibility to infections shown by different Races of the same Species. Ex. Algerian sheep is resistant to Anthrax; Negroes in USA are more susceptible to TB than the Whites. Individual Immunity: Difference in susceptibility to infection exhibited by different individuals in the same Race. Ex. Every individual responds to the same pathogen differently; Homozygous twins show similar response to a pathogen, which is not seen with Heterozygous Twins
  13. 13. DWD 14 Innate (Native) Immunity Factors influencing the level of Innate Immunity in an individual: Age: Two extremities of life – most susceptible to infections; Fetus in utero – protected from maternal infections by placental barrier; (exceptional infections – ToRCH Group) Young ones – susceptible to infections due to hormonal Influence ex. Gonococcal infection in prepubertal girls; Old age – highly susceptible to infections due to waning of their Immune Response.
  14. 14. Factors influencing the level of Innate Immunity in an individual contd….. Hormones: Endocrine disorders such as Diabetes mellitus, Hypothyroidism and Adrenal dysfunction – assoc. with enhanced susceptibility to infections; Corticosteroids depress host’s resistance due to their anti- inflammatory and anti-phagocytic effects, and suppress Ab. formation and Hypersensitivity; Elevated Steroid level in Pregnancy or Stress – increased susceptibility to infections; Beneficial effect – neutralize the harmful effect of bacterial products such as Toxins. DWD 15 Innate (Native) Immunity
  15. 15. Factors influencing the level of Innate Immunity in an individual Contd….. DWD 16 Innate (Native) Immunity Nutrition: Balanced Diet – Good Health; Malnutrition reduces Immune Response; Severe protein deficiency – decreased CMI; Some viruses may not multiply in the tissues of severely malnourished individuals.
  16. 16. DWD 17 Innate (Native) Immunity Mechanisms of Innate Immunity:
  17. 17. 1. Epithelial Surfaces The intact Healthy Skin & Mucus Membrane covering the body confers protection against invasion of pathogens. Healthy Skin: Intactness of Skin – mechanical barrier; Drying sweat & sebaceous secretions – high conc. of salt – bactericidal; Resident bacterial flora – interferes with the invasion of the pathogens. DWD 18 Mechanism of Innate Immunity
  18. 18. 1. Epithelial Surfaces contd ………. Mucosa of the Respiratory Tract: The very architecture of the nose prevent entry of the Microorganisms inhaled particles arrested near the nasal orifices; Ciliary movement of hairs – leads to Sneezing reflex; Those that pass beyond are held back by the Mucus lining the epithelium, and are swept back to the pharynx – swallowed or Coughed off – Cough Reflex Particles that reach the lungs – captured by the Alveolar Macrophages in the pulmonary alveoli – destroyed by the phagocytic cells. DWD 19 Mechanism of Innate Immunity
  19. 19. 1. Epithelial Surfaces contd ………… Mouth: Constantly bathed in saliva – inhibitory effect on many Microorganisms; Particles swallowed – in the stomach subjected to digestive juices; From the Duodenum to the Ileum, the pH becomes more alkaline (with rich & varied bacterial flora) ; Intestinal mucosa – covered with a lace-like Network of mucus – particles enmeshed to form small masses – propelled by peristalsis; Normal intestinal flora – protects & prevents Colonisation of the pathogen. DWD 20 Mechanism of Innate Immunity
  20. 20. 1. Epithelial Surfaces contd ………… Conjunctiva: Flaccid movement of Eyelids & flushing action of lachrymal secretions eliminates microorganisms; Tears contain lysozymes (Fleming – 1922) – antibacterial subs; act as muraminidase; Lysozymes – present in tissue fluids & nearly all Secretions; & also in Phagocytic cells. (except CSF, sweat & Urine) DWD 21 Mechanism of Innate Immunity
  21. 21. 1. Epithelial Surfaces contd ………… Urinary Tract: Flushing action of Urine eliminates microorganisms from the Urethra; Spermine & Zinc in Semen – bactericidal; Acidity of adult vagina & resident aciduric bacilli – fermentation of glycogen – unfavorable for many pathogens – inhibit colonisation. DWD 22 Mechanism of Innate Immunity
  22. 22. 2.Antibacterial Substances in Blood & Tissues : The Complement System: Bactericidal activity. A group of cell murdering proteins. Properdin in serum + C + Mg++ ions – lysis of GNB & also inactivates Viruses; Other subs having bactericidal activity, in the blood & tissues are – ß-Lysin, Lukins (excreted by Leucocytes), Plakins (by Platelets) & Lactic acid (in muscle tissues & in inflammatory zone). Interferons – produced by cells stimulated by live or killed viruses or other inducers – a very important defence against viral infections. DWD 23 Mechanism of Innate Immunity
  23. 23. 2.Antibacterial Substances in Blood & Tissues : The Pattern Recognizing molecules : Many of the molecules involved in innate immunity have the property of pattern recognition, the ability to recognize a given class of molecules .Because certain types of molecules are unique to microbes and never found in multicellular organisms, the ability to immediately recognize and combot invaders displaying such molecules is a strong feature of innate immunity. DWD 24 Mechanism of Innate Immunity
  24. 24. 2.Antibacterial Substances in Blood & Tissues : The Pattern Recognizing molecules : Once a pathogen breaches the non specific barriers of the host, infection & disease may ensue. The immune system responds to invasion with two critical functions - sensors detect the invader,& an elaborate response mechanism attacks the invader. The first detection event of the immune response occurs when the invader interacts with soluble or membrane bound molecules of the host capable of precisely discriminating between self(host) & nonself(pathogen) . The molecular sensors recognize motifs that are highly conserved within a microbial species( & are usually necessary for survival) but are generally absent from the host. Because they recognize particular overall molecular patterns, such receptors are called pattern recognition receptors(PRRs), & when such patterns are found on pathogens, they are called pathogen associated molecular patterns(PAMPs). DWD 25 Mechanism of Innate Immunity
  25. 25. 2.Antibacterial Substances in Blood & Tissues : The PAMPs recognized by PRRs include combinations of sugars, certain proteins, particular lipid bearing molecules & some nucleic acid motifs. Detection of pathogen associated molecular patterns by soluble & membrane bound mediators of innate immunity brings multiple components of immunity into play. The soluble mediators include initiators of the complement system , such as mannose – binding lectin(MBL) & C – reactive protein(CRP). DWD 26 Mechanism of Innate Immunity
  26. 26. 3.Microbial Antagonism : Resident bacterial flora of the Skin, Respiratory Tract, Intestine & Urinary Tract do not allow the pathogens to colonise the surface. Alteration in the normal flora leads to susceptibility to infection; Seen in cases with the long-term use of oral antibiotics (usually in high doses) may lead to Staphylococcal or Clostridial Enterocolitis. DWD 27 Mechanism of Innate Immunity
  27. 27. 4. Cellular Factors in Innate Immunity : Phagocytic Cells: Metchnikoff – (1922) Microphages – PMN leucocytes, Macrophages – Histiocytes (Wandering amoeboid cells in the tissues, Fixed RE cells, Monocytes in blood) Capsulated bacteria (ex. Pneumococci) – not readily phagocytosed except in the presence of Opsonin; Some bacteria (Lepra bacilli, Tubercle bacilli, Brucella etc) resist intracellular killing – instead, may multiply in the phagocytic cells – may disseminate. DWD 28 Mechanism of Innate Immunity
  28. 28. 4. Cellular Factors in Innate Immunity : Fever: Rise in body temperature – a natural defence mechanism Accelerates physiological processes; May even destroy some pathogens; (treatment of Syphilis with MP infection before discovery of Penicillin) Fever stimulates production of Interferons & helps in recovery of viral infections. DWD 29 Mechanism of Innate Immunity
  29. 29. 4.Cellular Factors in Innate Immunity : Acute Phase Protein: Infection or injury leads to a sudden increase in the plasma conc. of certain proteins, collectively called Acute Phase Proteins. These include : C-Reactive Protein (CRP); Properdin system; Mannose-Binding Protein (MBP), α-1 acid glycoprotein, serum amyloid P component, etc. These may activate Alternate Complement Pathway; They are believed to enhance host resistance, prevent tissue injury & promote repair of inflammatory lesions. DWD 30 Mechanism of Innate Immunity
  30. 30. 4.Cellular Factors in Innate Immunity : Toll – like Receptors: Most of the molecules involved in innate immunity have the property of pattern recognition , the ability to recognise a given class of molecules. Certain molecules are unique in microbes & never found in multicellular organisms. To recognise these patterns & to destroy the invaders displaying such molecules is a feature of innate immunity. Such molecules are a class of cell – associated receptors & known as Toll – like receptors. 13 different TLRs present that recognise pathogens & enhance phagocytosis & lead to inflammation at the site. DWD 31 Mechanism of Innate Immunity
  31. 31. DWD 32 Innate (Native) Immunity