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Immunological reactions and immune response ppt



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  • Haptens:- Low molecular weight substances - These substances not immunogenic by itself- If couple to a larger carrier molecule e.g. (albumin, globulins) they become immunogenic- Examples : simple chemicals and drugs: penicillin, sulphonamid, aspirin, cosmetic, tranquillizers, neomycin skin ointment
  • 33.0.1. The Immune System Adapts, Using the Principles of EvolutionThe immune system comprises two parallel but interrelated systems. In the humoral immune response, soluble proteinscalled antibodies (immunoglobulins) function as recognition elements that bind to foreign molecules and serve asmarkers signaling foreign invasion (Figure 33.1). Antibodies are secreted by plasma cells, which are derived from Blymphocytes (B cells). A foreign macromolecule that binds selectively to an antibody is called an antigen. In aphysiological context, if the binding of the foreign molecule stimulates an immune response, that molecule is called animmunogen. The specific affinity of an antibody is not for the entire macromolecular antigen but for a particular site onthe antigen called the epitope or antigenic determinant.In the cellular immune response, cells called cytotoxic T lymphocytes (also commonly called killer T cells) kill cells thatdisplay foreign motifs on their surfaces. Another class of T cells called helper T lymphocytes contributes to both thehumoral and the cellular immune responses by stimulating the differentiation and proliferation of appropriate B cells andcytotoxic T cells. The celluar immune response is mediated by specific receptors that are expressed on the surfaces of theT cells.The remarkable ability of the immune system to adapt to an essentially limitless set of potential pathogens requires apowerful system for transforming the immune cells and molecules present in our systems in response to the presence ofpathogens. This adaptive system operates through the principles of evolution, including reproduction with variationfollowed by selection of the most well suited members of a population.If the human genome contains, by the latest estimates, only 40,000 genes, how can the immune system generate morethan 108 different antibody proteins and 1012 T-cell receptors? The answer is found in a novel mechanism for generatinga highly diverse set of genes from a limited set of genetic building blocks. Linking different sets of DNA regions in acombinatorial manner produces many distinct protein-encoding genes that are not present in the genome. A rigorousselection process then leaves for proliferation only cells that synthesize proteins determined to be useful in the immuneresponse. The subsequent reproduction of these cells without additional recombination serves to enrich the cellpopulation with members expressing a particular protein species.


  • 1. • Any substance which introduced parenterally into the body, stimulates the production of an antibody with which it reacts specifically and in an observable manner ANTIGEN
  • 2. 1. Induction of an immune response 2. Specific reaction with antibodies
  • 3. 1. Induction of an immune response 2. Specific reaction with antibodies Complete antigen Hapten
  • 4. The smallest unit of antigenicity is known as epitope Smallest area 4-5 amino acids or monosaccharide residues Specific chemical structure, charge and configuration Antibodies are specific for epitopes
  • 5. Antibodies or Immunoglobulins Immunoglobulin Provides Structural and Chemical concept Antibody Is a biological and functional concept All antibodies are Immunoglobulins, but all Ig may not antibodies
  • 6. Antigen-Antibody Reaction The reaction serve several purposes In vivo In vitro Immunity , Autoimmune diseases Serological reactions
  • 7. Primary Secondary Tertiary
  • 8. The reaction is specific Entire molecule react and not fragment There is no denaturation of Ag or Ab Combination occurs at the surface Combination is firm but reversible Both Ag and Ab participate in the reaction Ag-Ab can combine in varying proportions
  • 9. In terms of MASS(mg nitrogen ) or as units or titer
  • 10. • Highly sensitive – False negative reactions are absent or minimal Sensitivity • Highly specific – False positive reactions are absent or minimal Specificity
  • 11. Precipitation reaction Agglutination Complement fixation test Neutralisation test Opsonisation Immunoflurorescence Radioimmunoassay Enzyme Immunoassays Chemiluminescence immunoassay Immunoelectroblot Techniques Immunochromatographic tests Immunoelectronmicroscopic tests
  • 12. Precipitation occurs Electrolyte Antibody Soluble antigen Precipitation reaction
  • 13. • Flocculation • Medium • The amount of precipitation influenced by relative proportion of Ag and Ab • Mechanism of precipitation - Prozone - Zone of equivalence - Postzone Precipitation reaction
  • 14. Precipitation reaction Application: Both qualitative and quantitative tests Very sensitive in detecting antigens Forensic application
  • 15. Precipitation reaction Ring test Slide test Tube test Immunodiffusion Electroimmunodiffusion
  • 16. Immunodiffusion 1. Single diffusion in one direction 2. Double diffusion in one direction 3. Single diffusion in two dimension 4. Double diffusion in two dimension 5. Immunoelectrophoresis
  • 17. Radial Immunodiffusion (Mancini) • Interpretation – Diameter of ring is proportional to the concentration • Quantitative – Ig levels – Screaning sera for Abs to influenza virus among others • Method – Ab in gel – Ag in a well Ag Concentration Diameter2 AgAgAgAg Ab in gel
  • 18. Double diffusion in 2 dimensions
  • 19. • First do electrophoretic separation of a mixture of soluble antigens in a gel medium. • Individual antigens are detected using an antiserum containing antibodies for all antigens in the mixture diffused at a right angle to the direction of electrophoresis.
  • 20. Antigen applied to wells; Separation by charge Antibody in trough, Protein diffusion in gel Precipitin complex indicating identity and recognition 1 2 3 Example: Human sera probed with rabbit anti-human antibodies AgAg
  • 21. • Development of precipitin lines can be speeded up by electrically Various methods A. One dimensional double electroimmunodiffusion • Counter immunoelectrophoresis B. One dimensional single electroimmunodiffusion • Rocket electrophoresis
  • 22. A. One dimensional double electroimmunodiffusion [Counter immunoelectrophoresis] Clinical application: detecting various Ags; α-fetoprotein in serum& specific Ags of Cryptococcus & Meningococcus in the CSF
  • 23. Slide agglutination Tube agglutination Antiglobulin test Passive agglutination Haemagglutination Applications
  • 24. +  Patient’s RBCs Coombs Reagent (Antiglobulin)
  • 25. Patient’s Serum Target RBCs +  Step 1 +  Coombs Reagent (Antiglobulin) Step 2
  • 26. • The ability of Ag-Ab complex to fix complement is made use of in CFT • Looking for evidence of infection. • The test requires five reagents and is carried out in two steps. • The Wassermann test is one form of complement fixation test: serodiagnosis of syphilis.
  • 27. • Based on the concept that antibodies can neutralize biological activity of many pathogens and their toxins Viral neutralisation test Toxin neutralisation test
  • 28. Heat labile substance Heat stable substance Complement Bacteriotropin Opsonin
  • 29. Albert Hewett Coons (1912–1978) Direct Immunofluorescence test Indirect Immunofluorescence test
  • 30. • 1957 – Berson and Yalow • Application – Hormone - Drugs - Tumour markers - IgE - Viral antigens Nobel Prize 1977
  • 31. – Sensitivity - Simplicity - Economy - Absence of radiation - Availability of test kit - Facility for automation
  • 32. • Includes all assays based on measurement of enzyme labeled antigen, hepten or antibody 2 types Homogeneous EIA Heterogeneous EIA
  • 33. • Technique involves the use of an IMMUNOSORBENT • Usually done using 96-well microtitre plates suitable for automation – Rota virus - Anti -HIV antibody test
  • 34. • Refers to a chemical reaction emitting energy in the form of light • Chemiluminescent compounds - LUMINOL - ACRIDINIUM ESTERS • The method has been fully automated
  • 35. • Combine the sensitivity of EIA with much greater specificity • Combination of 3 separate procedures Separation Blotting EIA or RIA
  • 36. • One step • Qualitative - Simplicity - Economy - Reliability • HBSAg detection
  • 37. The key is our ability to produce more than 108 distinct antibodies and more than 1012 T-cell receptors
  • 38. The immune system has 2 arms Innate immunity Adaptive immunity
  • 39. 1. Humoral (AMI) 2. Cellular (CMI)
  • 40. Humoral Immune response(AMI) Entry Processing Secretion
  • 41. Lag phase Log phase Plateau or steady state Phase of decline
  • 42. Non- immune phase Phase of immune elimination
  • 43. • Immune response to an antigen is brought about by 3 type of cells Lymphocytes APC Effector cells
  • 44. © Ranjith’s
  • 45. © Ranjith’s
  • 46. Genetic Age Nutrition Route of administration Size & number of doses Multiple antigens Adjuvants Immunosuppres sive drugs Effect of antibody
  • 47. Specific immune response that do not involve antibodies. Delayed hypersensitivity Immunity in infections Transplantation immunity Immunological surveillance Autoimmune disease Scope of CMI
  • 48. • Antigenic stimulus • Only T-cell dependant antigens lead to CMI • T-cell bears specific receptor on its surface • T cells recognize antigens only when presented with MHC molecules • Helper T-cells • Cytotoxic T-cells
  • 49. • Peptide mediators or intracellular messengers which regulate immunological, inflammatory and reparative host responses • They are potent hormone like substances • Produced by lymphocytes, macrophages, platelets & fibroblasts
  • 50. Interleukins Colony stimulating factors Tumour necrosis factors Interferons Others
  • 51. Macrophages & other cells • IL-1α and IL-1β Proliferation & differentiation of T, B and other cells Pyrogenic Induce acute phase proteins Bone marrow cell proliferation Interleukin-1
  • 52. T-cells • Powerful modulator of the immune response Promote growth and differentiation of T and B cells Cytotoxicity of T and NK cells Secretions of other lymphokines Interleukin-2[TCGF]
  • 53. • Stimulates the growth & differentiation of pleuripotent stem cells in the bone marrow • Responsible for adjusting the rate of production of blood cells • Treating hematopoietic dysfunctions in infections & malignancies Colony stimulating factors
  • 54. • Induce hemorrhagic necrosis in certain tumours TNFα and TNFβ • Cachectin is TNFα Tumour necrosis factors
  • 55. • Originally identified as antiviral agents  Interferons