BASIC IMMUNOLOGY Dr Akpor - PowerPoint Presentation

1. BASIC IMMUNOLOGYDr Akpor OA

2. OBJECTIVESAt the end of the lecture, students will be able to:Explain the role of the immune systemDescribe the two types of immunityExplain antibodies and its various typesDefine immunodeficiency

3. DEFINITIONSImmune system: cells, tissues, and molecules that mediate resistance to infections Immunology: study of structure and function of the immune systemImmunity: resistance of a host to pathogens and their toxic effectsImmune response: collective and coordinated response to the introduction of foreign substances in an individual mediated by the cells and molecules of the immune system

4. ROLE OF THE IMMUNE SYSTEMDefense against microbesDefense against the growth of tumor cellskills the growth of tumor cellsHomeostasisdestruction of abnormal or dead cells (e.g. dead red or white blood cells, antigen-antibody complex)

5. IMMUNE SYSTEMOrgansCellsMolecules

6. Immune System:(1) organsTonsils and adenoidsThymusLymph nodesSpleenLymphiod tissueAppendixLymphatic vesselsBone marrow

7. IMMUNE SYSTEM:(2) CELLSLymphocytesT-lymphocytes B-Lymphocytes, plasma cells natural killer cellsMonocytes, MacrophageGranulocytesneutrophils eosinophils basophils

8. IMMUNE SYSTEM:(3) MOLECULES Antibodies Complement proteinsCytokinesInterleukines InterferonsTNF

9. TWO TYPES OF IMMUNITY Innate (non-adaptive)first line of immune responserelies on mechanisms that exist before infectionAcquired (adaptive)Second line of response (if innate fails)relies on mechanisms that adapt after infection handled by T and B lymphocytesone cell determines one antigenic determinant

10. INNATE IMMUNITYBased on genetic make-up Relies on already formed componentsRapid response: within minutes of infectionNot specificsame molecules / cells respond to a range of pathogensHas no memory same response after repeated exposure

11. Innate immunity: mechanisms Mechanical barriers / surface secretionskin, acidic pH in stomach, ciliaHumoral mechanisms lysozymes, basic proteins, complement proteins, interferons, TNFCellular defense mechanisms natural killer cells neutrophils, macrophages, mast cells, basophils, eosinophils

12. Adaptive immunity: second line of response Based upon resistance acquired during lifeRelies on genetic events and cellular growth Responds more slowly, over few days Is specificeach cell responds to a single epitope on an antigen Has anamnestic memoryrepeated exposure leads to faster, stronger response

13. Adaptive Immunity: active and passive

14. Adaptive immunity: mechanismsCell-mediated immune response (CMIR)T-lymphocyteseliminate intracellular microbes that survive within phagocytes or other infected cellsHumoral immune response (HIR)B-lymphocytesmediated by antibodieseliminate extra-cellular microbes and their toxins Plasma cell (Derived from B-lymphocyte, produces antibodies)

15. TYPES OF ADAPTIVE IMMUNITYNatural acquired active immunity; resulting from infection naturally this type of immunity may be long-lasting.Natural acquired passive immunity Antibodies transferred from a mother to a fetus (trans placental transfer) or to a newborn in colostrum results in naturally in the newborn; can last up to a few months.Artificially acquired active immunity Immunity resulting from vaccination can be long-lasting.Artificially acquired passive immunity refers to humoral antibodies acquired by injection;can last for a few weeks.

16. Cell-mediated immune responseT-cell recognizes peptide antigen on macrophage in association with major histo-compatibility complex (MHC) class Identifies molecules on cell surfaces Helps body distinguish self from non-selfT-cell goes into effectors cells stage that is able to kill infected cells

17. T lymphocytes2 typesHelper T- lymphocytes (CD4+)CD4+ T cells activate phagocytes to kill microbesCytolytic T-lymphocyte (CD8+)CD8+ T cells destroy infected cells containing microbes or microbial proteins

18. Cell mediated immune responsePrimary response production of specific clones of effector T cells and memory clonesdevelops in several days does not limit the infectionSecondary response more pronounced, faster more effective at limiting the infectionExample - cytotoxic reactions against intracellular parasites, delayed hypersensitivity (e.g., Tuberculin test) and allograft rejection

19. Humoral immune responseB lymphocytes recognize specific antigens proliferate and differentiate into antibody-secreting plasma cellsAntibodies bind to specific antigens on microbes; destroy microbes via specific mechanismsSome B lymphocytes evolve into the resting state - memory cells

20. Antibodies (immunoglobulins)Belong to the gamma-globulin fraction of serum proteinsY-shaped or T-shaped polypeptides 2 identical heavy chains2 identical light chainsFive kinds of antibodiesIgG, IgM, IgA, IgD, IgE (GMADE)

21. IgG70-75% of total immuniglobulinSecreted in high quantities in secondary exposures Cross the placentaNeutralize microbes and toxins Opsonize antigens for phagocytosisActivate the complement proteinsProtect the new-born

22. IgMSecreted initially during primary infection Cannot cross the placentaSecreted first during primary exposure Used as a marker of recent infection Presence in new-born means infectionSingle positive sample in serum or CSF indicates recent or active infection Used to detect early phase of infection

23. IgADimeric ( a molecule composed of two identical, simpler molecules) with secretory component in the lumen of the gastro-intestinal tract and in the respiratory tractNeutralizes microbes and toxinsSero-diagnosis of tuberculosisSynthicial respiratory virus tests

24. IgD MonomericPresent on the surface of B lymphocytesFunctions as membrane receptor Role unclearHas a role in antigen stimulated lymphocyte differentiation

25. IgE MonomericAssociated with anaphylaxisPlays a role in immunity to helmintic parasitesSero-diagnosis of infectious and non infectious allergies(e.g., allergic bronchopulmonary aspergillosis, parasitic diseases)

26. Failure of immune responseImmune response helps individuals defend against:microbes Some cancersImmune response can failHypersensitivity reactionsImmunodeficiency

27. Hypersensitivity reactionsCause cell damage through excessive immune response to antigensHypersensitivity Overreaction to infectious agentsAllergyOverreaction to environmental substancesAutoimmunityOverreaction to self

28. ImmunodeficiencyLoss or inadequate function of various components of the immune system Can occur in any part or state of the immune system physical barrier, phagocytes, B lymphocytes, T lymphocytes, complement, natural killer cellsThe immuno-compromised host has an impaired function of immune system is at high risk of infection

29. ImmunodeficiencyCongenital (primary) immunodeficiency genetic abnormality defect in lymphocyte maturationAcquired (secondary) immunodeficiency results from infections, nutritional deficiencies or treatments e.g AIDS, chronic leukemia

30. Summary (1)Innate immunityRelies on mechanisms already existing before microbe infects host Is the first line of defence Has no memory for subsequent exposureRelies on non specific mechanisms

31. Summary (2)Adaptive immunity Develops following entry of microbe into the hostComes into action after innate immunity fails to get rid of microbeHas memory to deal with subsequent exposureHappens through specific cellsT cells (cell mediated) B cells (antibody mediated)

32. Summary (3)Primary immune response Short lastingSmaller in magnitudeSecondary immune response Longer in duration Larger in magnitude Develop ‘memory cells’ following primary responseFailure of immune response can result in:Hypersensitivity Immunodeficiency