Immunodiagnosis and Immunopathology 2024 PDF

Introduction to Immunodiagnosis and Immunopathology Dr. Carla-Maria Alexander  Immunodiagnosis Diagnosis of disease based on antigen- antibody reactions Diagnosis of Detect antibodies to the infectious agent and confirm it as a suspect In...

Introduction to Immunodiagnosis and Immunopathology Dr. Carla-Maria Alexander  Immunodiagnosis Diagnosis of disease based on antigen- antibody reactions Diagnosis of Detect antibodies to the infectious agent and confirm it as a suspect Infectious Diseases Detect pathogen-specific IgM and confirm it as a recent visitor Detect pathogen-specific IgG as evidence of prevalence in a population Use the Antibody to detect the pathogen, use the Pathogen to detect the Antibody 30 Yr old male Sudden onset: high fever, night sweats, body pains, retro-orbital pain, chills Goes to Health Centre- next day Test for Dengue requested from Lab Hospitalised Dengue test returns negative-Discharged 7 days later dies Post mortem- dengue test requested from different lab –returns positive Virus Isolation Dengue IgM Dengue IgG  Agglutination is the process that occurs if an antigen is mixed with its corresponding antibody. Agglutination Agglutination may be visualised using cells (haemagglutination) or man- made latex particles (particle agglutination) AGGLUTINATION  https://www.biologycorner.com/anatomy/blood/notes_bloodtype.html Place a drop of blood on a card that will react to a serum on the card that contains antibodies. PCR https://external-content.duckduckgo.com/iu/?u=https%3A%2F%2Fwww.tagar.id%2FAsset%2Fuploads2019%2F1585291294646-pcr.jpg&f=1&nofb=1 ELISA – Enzyme-Linked Immunosorbent Assay A plate-based assay technique designed for detecting and quantifying substances such as peptides, proteins, antibodies and hormones An Ag must be immobilised on a solid surface and then complexed with an antibody that is linked to an enzyme Detection is accomplished by assessing the conjugated enzyme activity via incubation with a substrate to produce a measurable product MOST IMPORTANT: a highly specific antibody-antigen interaction https://www.slideshare.net/dream10f/immunologic-laboratorytests  ELISA readers or micro plate readers do spectrophotometry; they emit light at one wavelength, and measure the amount of light absorbed and reflected by an object such as a protein. A spectrophotometer measures ultraviolet and visible light. ELISA plate readers can also measure fluorescence and luminescence. Chemical dyes fluoresce or emit one color or wavelength when exposed to light. The amount of reflection, absorption and the colour identify, and measure the amount of a substance. Immunopathology Illness or disease due to defects in the Innate or Adaptive Immune Response  An overactive immune response - Hypersensitivity An ineffective immune response – Immunopathology Immunodeficiency An inappropriate action to self - Autoimmunity Autoimmunity This Photo by Unknown author is licensed under CC BY-SA.  How does the Are there Can the immune immune system mechanisms that response be distinguish prevent immune induced to a state between these two responses against of states? harmless antigens? unresponsiveness? We have the ability to recognise “self” We have the ability to eliminate “non-self” We must not attempt to eliminate “self” This distinction requires an active process on the part of the immune system  It does NOT affect our ability to respond to The state of specific non- foreign antigens and is responsiveness to self different from the state of antigens is known as general immunological tolerance unresponsiveness known as ANERGY  The most important tolerance is self- tolerance  This occurs in the developing foetus during normal immune ontogeny  Tolerogen TOLERANCE  An antigen that induces tolerance  Tolerance is antigen and cell specific  Only occurs for the tolerogen that induced it  Continued response to other antigens   B and T cells need to be educated to be tolerant and this occurs in the central and peripheral lymphoid organs and tissues  The processes ideally result in lymphocytes that are Central vs immunocompetent or tolerant peripheral towards encountered antigens tolerance  The mechanisms of tolerance induction and maintenance vary between the cell type and the location Central & Peripheral tolerance Thymic development  Occurs in tandem with Central tolerance  Not all autoAgs are expressed in the thymus  Several autoreactive T cells are found in the periphery  Peripheral tolerance mechanisms exist to eliminate or suppress autoreactive T cells that escape to the periphery  Mechanisms:  Deletion  Ignorance -  Anergy  Immune regulation Central & Peripheral tolerance  At the immature B cell stage, the BCR is tested for the first time for reactivity against autoantigens  BCR reacts with high avidity – Apoptosis occurs  BCR reacts with low to medium avidity – Receptor editing or Anergy occurs  The autoreactive B cell reactivates recombinase activating genes (RAGs) Ig gene rearrangement to form a non-autoreactive BCR.  The new BCR is tested again for autoreactivity.  Nonproductive receptor editing leads to clonal deletion of the autoreactive B cell Peripheral tolerance mechanisms are necessary:  T-independent B cells can be activated by autoantigens without T cell help  Molecular mimicry can lead B cells to produce cross-reactive Abs  BCRs are hypermutated upon activation, thus they may become reactive  Important in maintaining homeostasis and can also secrete Abs.  Origin is not fully understood  Development is induced by various activites including Inflammation, presence of apoptotic cells, tumour related TNFa  Actions include secretion of regulatory cytokines: IL-10, TGFb and expression of regulatory enzymes  Results : inhibition of T cell proliferation, suppression of TH1 and Th17 cytokine production, T reg induction, inhibition of DC and Macs functions  B-regs have been implicated in autoimmunity, allergy, cancer and transplantation in murine experimental models  Types of hypersensitivity reactions Type Alternate name Examples Mediators I Allergy (immediate) Atopy IgE – Anaphylaxis – Asthma – Allergic rhinitis – Angioedema – Food allergy II Cytotoxic, antibody- Erythroblastosis IgG, IgM dependent fetalis Goodpasture syndrome Autoimmune anemias, thrombocytopenias III Immune complex Systemic lupus Aggregation of disease erythematosus antigens Serum sickness IgG, IgM Reactive arthritis Complement proteins Arthrus reaction IV Delayed-type Contact dermatitis T cells, monocytes, hypersensitivity, cell- Tuberculosis macrophages mediated, antibody- Chronic transplant independent rejection  Immunodeficiency refers to a state in which the immune system’s ability to fight infectious disease is compromised or entirely absent. Immunodeficiency disorders may result from a primary genetic defect (primary immunodeficiency which can effect either innate or acquired immune function through inhibition of selected immune cells or pathways, or it may be acquired from a secondary cause (secondary immunodeficiency), such as viral or bacterial infections, malnutrition, autoimmunity or treatment with drugs that induce immunosuppression. Certain diseases can also directly or indirectly impair the immune system such as leukemia and multiple myeloma. Immunodeficiency is also the hallmark of acquired immunodeficiency syndrome (AIDS), caused by the human immunodeficiency virus (HIV). HIV directly infects Th cells and also impairs other immune system responses indirectly.  INFECTION Edward Jenner - England – 1796 -first modern vaccine Infected individual with a bovine analogue of smallpox, vaccinia (from vacca, Latin for cow), causing cowpox Belief that protective immunity against smallpox without risk of significant disease would be provided to humans Named the process Vaccination VACCINATION By Srcyr16 - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=40659361 INFECTION Louis Pasteur – 1879 - first modern attenuated vaccine Chickens infected with month old virulent chicken bacteria only showed mild signs of the disease Once well, chickens were re-infected with bacteria and did not become ill Pasteur became the first to take the attenuated vaccine to the laboratory Known as the birth of Immunology  IMMUNISATION THE PROCESS BY WHICH A PERSON IS MADE IMMUNE OR RESISTANT TO AN INFECTIOUS DISEASE, USUALLY BY THE ADMINISTRATION OF A VACCINE PASSIVE AND ACTIVE IMMUNISATION Passive : The injection/introduction of preformed antibodies or immune serum into a naïve recipient Active: The use of antigen to confer immunity Immune system has a role Immunological memory is developed PASSIVE IMMUNISATION Natural Passive Transfer of maternal Abs across the placenta to the developing foetus Maternal Abs present in colostrum and milk also provide passive immunity to the infant http://ib.bioninja.com.au/higher-level/topic-11-animal-physiology/111-antibody-production-and/types-of-immunity.html Passive Immunisation Artificial Passive Injecting a recipient with preformed Abs Routinely administered to individuals exposed to various threats Snake bites, rabies, tetanus, Varicella zoster, Hep A or B Antivenom is a mixture of hyperimmune globulins and other proteins obtained from the serum of animals (horses, sheep) that have been immunized with the venom of a snake. Hyperimmune globulins are concentrated immune globulins with specificity for an antigen, or group of antigens. https://www.quora.com/How-can-a-passive-immunity- Provides immediate protection to travelers/health- be-acquired care workers  Natural Active  Occurs when there is a natural infection with a microorganism http://ib.bioninja.com.au/higher-level/topic-11-animal-physiology/111-antibody-production-and/types-of- immunity.html Active Immunisation - Artificial Vaccines can elicit Abs and T cell responses Abs Can be Neutralising Abs Can activate complement Stimulate phagocytosis and NK cell-mediated killing CD8+ T cells Inhibit viral replication via interferons Kill infected cells http://ib.bioninja.com.au/higher-level/topic-11-animal-physiology/111-antibody-production-and/types-of-immunity.html IMMUNOLOGICAL BASIS OF VACCINATION www.lecturio.com  PASSIVE ACTIVE Injection of pre-formed Abs Injection of Ag; often requires additional components Protection is immediate but short-term Takes time to develop but provides long (Ab ½ life ~ 3 weeks) term protection – Memory B & T cells Only provides humoral immunity Potential to develop both a cell-mediated and humoral response Risk of adventitious pathogen transfer Immune response generated in vivo PASSIVE AND ACTIVE IMMUNISATION VACCINATION – HERD IMMUNITY A form of immunity that occurs when the vaccination of a significant portion of a population (herd) provides a measure of protection for individuals who have not developed immunity https://medium.com/@gidmk/herd-immunity-is-pretty-cool-adbc52630f9f VACCINATION Various types of vaccines that are currently in use or being researched Live, Attenuated Killed/ Inactivated Subunit Toxoid Nucleic Acid Recombinant Vector  COMPONENTS OF A VACCINE https://i0.wp.com/www.compoundchem.com/wp-content/uploads/2015/02/Medicinal-Chemistry-Common-Components-of- Vaccines-Summary.png?ssl=1  Accentuation of the response to an immunogen IMMUNOPOTENTIATION by administration of another substance. Adjuvants (Latin, “adjuvare,”) - meaning “to help” Adjuvants Designed to improve poorly immunogenic vaccines. Adjuvants affect the immune response in various ways:  To increase the immunogenicity of weak antigens  To enhance speed and duration of immune response  To stimulate and modulate humoral responses, including antibody isotype  To stimulate cell-mediated immunity  To improve induction of mucosal immunity  Enhance immune responses in immunologically immature patients, particularly infants  To decrease the dose of antigen required; reducing costs and eliminating inconvenient requirements for booster shots  The act of transferring cells, tissues and/or TRANSPLANTATION C organs (a graft) from one site to another https://www.donornetworkwest.org/organ-donation-facts- statistics/#1609281777179-6a497bfa-9c5b  TYPES OF C TRANSPLANTS http://www.brainkart.com/media/extra/dcVyW 3W.jpg  Damage is irreversible/alternative treatments are not applicable Disease must not recur Renal transplant for Goodpasture syndrome patient with antiglomerular basement membrane Abs The chances of rejection must be minimised Donor & recipient should be ABO compatible* Recipient should not have anti-donor-specific HLA Abs Donor should be as close as possible HLA match to recipient* Patient must take immunosuppressive treatment Criteria for Organ Transplantation  Both CD4+ and CD8+ have a role Key cell in Removal of one or the other still led to rejection Graft Removal of both led to long-term rejection survival of allografts Non-T cell Immune Responses Donor-specific Abs – antibodies against graft antigens – contribute to rejection MHC antigens on endothelial cells lead to alloantibody –mediated damage against graft vasculature Ischemic damage due to interruption of blood supply to tissues & organs Expression of DAMPs in the graft, stimulating innate responses which can Directly cause grat injury Increasing migration of lymphocytes into the graft, activation APCs, & NK cells Tolerated Allograft Mammalian foetus Carries paternal MHC and minor HC Ags Not rejected by mother Research at NYU School of Medicine in 2012 partially answered Why? Onset of pregnancy, chemokine genes responsible for recruiting immune cells to the sites of inflammation are turned off within the decidua Decidua – specialised structure that encases the foetus and placenta T cells are not able to accumulate in decidua, thus no attack of the foetus  The reaction of grafted mature T cells with alloantigens of the recipient The host is immunocompromised Graft vs Host Directed against minor histocompatibility Ags usually Disease Occurs in bone marrow transplants mostrly  Pharmacologic agents used for prevention and treatment include non- specific immunosuppressive and T cell specific immunosuppressive drugs. Non-specific examples Graft vs Host Corticosteroids – may affect the release of IL-2 & IFN-γ Disease Methotrexate – affects activated T cells; reduces proliferation T cell specific examples Cyclosporine Tacrolimus Find Out Immunogenicity Antigenicity Epitope Antigen