Presentation on theme: "Applied Immunology Lecture notes"— Presentation transcript:
1 Applied ImmunologyLecture notesAftab Jasir: European Centre for Disease Prevention and Control (ECDC)European Public Health Microbiology training program (EUPHEM)Introductory course, Menorca,2012
2 ObjectivesDefine basic components of immunologyDescribe important terms in immunologyExplain major applications of immunology
3 What is immunology?Immunology is a broad branch of biomedical science that covers the study of all aspects of the immune system in all living organisms.It deals with the physiological functioning of the immune system in states of both health and diseaseThe specificity of the bond between antibody and antigen has made it an excellent tool in the detection of substances in a variety of diagnostic techniques. Antibodies specific for a desired antigen can be conjugated with a radiolabel, fluorescent label, or color-forming enzyme and are used as a "probe" to detect it. However, the similarity between some antigens can lead to false positives and other errors in such tests by antibodies cross-reacting with antigens that aren't exact matches
4 The immune system is the ministry of defence of the human/animal body What is the immune system?The immune system is the ministry of defence of the human/animal body
5 Immunologically Naive No previous experienceNo memoryMust be educated
6 Immunodeficiency and Immunosuppression Immunodeficiencyis a state in which the immune system's ability to fight infectious disease is low or entirely absent.Immunosuppression involves an act that reduces the activation or efficacy of the immune system. immunosuppression may occur as an adverse reaction to treatment of other conditions.
7 Major defence components of the human immune system CellsImmunoglobulins
8 Overview of the immune system Innate (nonspecific)1st line of defenseCellular componentsHumoral componentsAdaptive(specific)2nd line of defense
9 Definitions/terminology Antigens (Ag)Large molecules, is anything that obtain the formation of a specific immune response (Anomy)Ag determinants (epitopes) are the particular chemical groups on a molecule that are antigenicAntibody(Ab)/immunoglobulin (Ig).A special group of soluble proteins that are produced in response to foreign antigens (substances)Anomy and forgion
11 IgM (first exposure, large, not passing placenta, huge amont) 5 classes of IGsIgM (first exposure, large, not passing placenta, huge amont)IgG (secondary exposure, small, passing placenta)IgD (proteins in the plasma membranes of mature B-lymphocytes, same time as IgM)IgA (mucosal immunity, respiratory tract)IgE (Allergy and parasites)IgG is the most abundant immunoglobulin and is approximately equally distributed in blood and in tissue liquids, comprising 75% of serum immunoglobulins in humans, IgG molecules are synthesized and secreted by plasma B cells.Immunoglobulin A (IgA) is an antibody that plays a critical role in mucosal immunity. More IgA is produced in mucosal linings than all other types of antibody combinedIn biology, Immunoglobulin E (IgE) is a class of antibody (or immunoglobulin "isotype") that has only been found in mammals. IgE is a monomeric antibody with 4 Ig-like domains (CH1->CH4).  It plays an important role in allergy, and is especially associated with type 1 hypersensitivity. IgE has also been implicated in immune system responses to most parasitic wormsImmunoglobulin D (IgD) is an antibody isotype that makes up about 1% of proteins in the plasma membranes of mature B-lymphocytes where it is usually coexpressed with another cell surface antibody called IgM. IgD is also produced in a secreted form that is found in very small amounts in blood serum.
15 Primary and secondary antibodies P: antibodies raised against an antigenic target of interest and are typically unconjugated.S: antibody that binds to primary antibodies or antibody fragments. They are typically labeled with probes that make them useful for detection,Primary antibodies are antibodies raised against an antigenic target of interest (a protein, peptide, carbohydrate, or other small molecule) and are typically unconjugated (unlabelled).secondary antibody is an antibody that binds to primary antibodies or antibody fragments. They are typically labeled with probes that make them useful for detection
16 Immune Precipitation Antigen Antibody Study Guide Why do soluble antigens and antibodies precipitate?AntigenAntibody
17 Agglutination RBC RBC RBC IgM Antibody RBC RBC RBC RBC RBC Study GuideWhat is the difference between precipitation and agglutination?IgG AntibodyRBCRBCRBC
18 Factors influencing immunogenicity Contribution of immunogenContribution of biological systemMethod of administration
19 Class SwitchingBiological mechanism that changes a B cell's production of antibody from one class to another, for example, from IgM to IgG.antibody titerStudy GuideWhat is the significance of class switching?IgMIgGtime
20 Four phases of the primary response lag phase where no antibody is detectedlog phase in which the antibody titer rises logarithmicallyplateau phase during which the antibody titer stabilizesphase (decline) during which the antibody is cleared or catabilized
21 Kinetics of the Ab Response T-dependent Ag; 1o Response D a y s A f t e r I m m u n i z a t i o nA b T i t e rLAGLOGDECLINEPLATEAULagLogPlateauDecline
22 Kinetics of the Ab Response T-dependent Ag; 2o Response 1o Ag2o AgD a y s A f t e r I m m u n i z a t i o nA b T i t e rLagLogPlateauDecline
23 Major practical applications of immunology Use of antiserum and vaccination to provide protection against disease.Diagnostic tool to detect disease.Epidemiological investigation of vaccine preventable diseases
25 My face is my fortuneWhere are you going, my pretty maid? I’m going a-milking, sir, she saidMay I go with you, my pretty maid? You’re kindly welcome, sir, she saidWhat is your father, my pretty maid? My father is a farmer, sir, she saidWhat is your fortune, my pretty maid? My face is my fortune, sir, she saidIllustration of the famous first vaccination experiment. In 1796 Edward Jenner infected eight-year-old James Phipps with fluid from a lesion on the hand of Sarah Nelmes, who had caught cowpox. The word ‘vaccination’ comes from the Latin word ‘vaccinia’ for cowpox. This was a successful experiment, because the boy was subsequently protected against a human smallpox infection. Years later Louis Pasteur proposed that all inoculations intended to protect against infectious diseases should be called vaccinations, in honour of Jenner.
27 VariolationThe word ‘variolation’ comes from the Latin word ‘variola’ for human smallpox.Figure 1. Ancient Oriental print illustrating the technique of variolation. Dried material from scabs of human smallpox is blown into the nose of an unaffected person with a small blowpipe. The word ‘variolation’ comes from the Latin word ‘variola’ for human smallpox.
28 Discovery of small pox vaccine In 1798, Jenner introduced 1st vaccination (vacca: cow) following his experimentation with isolates of cow pox virus from ‘Blossom’.Cartoon on smallpox vaccination from 1802 entitled “The Cow Pock or the Wonderful Effects of the New Inoculation”. It shows Edward Jenner and persons who are developing cow-like projections as a result of allowing themselves to be inoculated with an ‘animal diseaseEdward Jenner 1780ADBlossom28
33 Advantages and Disadvantages of Active Immunization Not immediateImmune suppressed/deficiencyLong term immunityHerd immunityRisk of infectionRisk of contaminationAnimal ???Attenuated can revert to their pathogenic form
34 Advantages and Disadvantages of Passive Immunization no long term protectionserum sicknessimmediate protectionrisk ofhepatitis and HIVgraft vs. host disease
35 Serological tests based on Abs specifically binding to Ag SerologyA science that attempts to detect signs of infection in a patient’s serum such as Ab for a specific microbeSerological tests based on Abs specifically binding to AgAg of known identity will react with Ab in an unknown serum sample.Known Ab can be used to detect Ag in serumAg-Ab reactions are visible by clumps, precipitates, color changes or release of radioactivity.The most effective tests have high specificity and sensitivity.
36 Enzyme (ELISA) Immunoassay Enzyme conjugated to anti-Ig antibody (“second antibody”)Addsubstratefor enzymeanti-antigenantibodyStudy GuideRadioimmunoassays (RIA) and Immunfluorescence Assays (IFA) depend on the detection of a radionuclide or a fluorescent probe attached to the second antibody, instead of the enzyme. In those cases, no substrate is needed.How would you use this assay to measure the concentration or detect the presence of an antigen?Antigen
37 a) The presence of a specific Ab b) Identification of microbes
38 Specificity, sensitivity, and cross reactivity a) SpecificityAb attaches with great exact-ness to only one type of Ag.b) SensitivityAb can locate Ag, even when it is greatly diluted.c) Cross reactivitythe ability of an individual antibody combining site to react with more than one antigenic determinant or the ability of a population of antibody molecules to react with more than one antigen.
39 Examples of serological tests Agglutination testsPrecipitation testsImmunoelectrophoresisWestern blot testsComplement fixation testsImmunofluorescence testingImmunoassays
40 agglutination is the clumping of particles agglutination is the clumping of particles. The word agglutination comes from the Latin agglutinare, meaning "to glue to."This occurs in biology in three main examples:The clumping of cells such as bacteria or red blood cells in the presence of an antibody. The antibody or other molecule binds multiple particles and joins them, creating a large complex.The coalescing of small particles that are suspended in a solution; these larger masses are then (usually) precipitated.An allergic reaction type occurrence where cells become more compacted together to prevent foreign materials entering them. This is usually the result of an antigen in the vicinity of the cells.
41 Acute infection Onset of symptoms Incubation Primary infection Days Modified from Hedman et al. 2000Primary infectionDaysWeeksMonthsYears
42 Acute infectionOnset of symptomsIgMIncubationPrimary infectionDaysWeeksMonthsYears
43 Acute virus infectionOnset of symptomsIgGIgMIncubationPrimary infectionDaysWeeksMonthsYears
44 Avidity = the sum of affinities between: antibodyandantigenAcute virus infectionOnset of symptomsIgG avidityIgMIgGIncubationPrimary infectionDaysWeeksMonthsYears
45 Secondary infection or reactivation Onset of symptomsIgG avidityIgMIgGIncubationPersistencePrimary infectionSecondary infection or reactivationDaysWeeksMonthsYears
46 Secondary infection or reactivation Onset of symptomsIgG avidityIgGIgMViremiaPrimary infectionSecondary infection or reactivationDaysWeeksMonthsYears
48 What should you have in mind!!! Tack home massage Some times Ag x Ab based tests can results in wrong alarm of outbreak ( Salmonella)Antigen variation is always a problem (Chlamydia, grouping of streptococci)Cross-reactivity can give wrong information of an outbreakAny unusual or unexpected results should be confirmed by genetic testIf possible use other methods than serology in an outbreak situation or combine with other methods