免疫2_精品文档.ppt

1、Immunity,State of protection against foreign organisms or substances(antigens)Defence against disease Defence against tumours,Figure 1,Immune responses are directed at our barriers with the environment,Innate Immunity,Non specific immune responses which include anatomic,physiologic,phagocytic and in

2、flammatory barriers that help prevent the entrance and establishment of infectious agents.These keep the invading pathogen at bay until a specific response can be made.,Acquired Immune responses,Specific response made against a particular pathogen or agentDiverse-responses can potentially be made ag

3、ainst any pathogen etc.Memory-the immune system can remember a pathogen that has previously infected the bodyEscalating response-and generates a faster more effective response next time!,How is this achieved?,2 inter-related events:recognition of antigenresponse to antigen,Figure 2,The immune system

4、 is compartmentalised to enable lymphocytes to come into contact with pathogens/antigens.,Antigen Presentation,Antigen presenting cells(dendritic cells,macrophages),B lymphocytes and T lymphocytes are involved in the generation of immune responses.Both B and T lymphocytes possess antigen receptors i

5、n their cell membrane.,B lymphocyte receptors(BCR),Antibody molecules bound to the cell membrane form the B cell receptor(BCR)BCR can recognise and internalise intact antigen.(antigen here can be a 3-dimensional structure),Figures 3 and 4,Structure of the B cell receptor,T lymphocyte receptors(TCR),

6、T lymphocytes only recognise antigen associated with MHC class I and class II moleculesantigen here is a short linear peptide-primary structure,Figures 5,6 and 7,Structure of the TCR and its interaction with MHC/peptide complexes,How are immune responses DIVERSE?,Each T and B lymphocyte has a DIFFER

7、ENT antigen receptorClonal expansion of a single cell results when the lymphocyte receptor meets its specific antigen.Expanded lymphocytes then develop different effector and memory functions,Function of T lymphocytes I,There are 2 major sub-populations.Helper T cells(Th)and cytotoxic T cells(Tc).Th

8、 cells express CD4 and recognise antigen+class II MHC(on antigen presenting cells).Antigen is a peptide of 18-22 amino acids,and is derived from proteins from outside the cell.fight extracellular pathogens.(can produce soluble mediators=cytokines.),Helper CD4 T lymphocytes,Functions of T lymphocytes

9、 II,Tc cells express CD8 and recognise antigen+class I MHC(on all body cells).Antigen is a peptide of 9 amino acids,and is derived from proteins synthesised inside the cell.Normally self peptides are expressed in class I MHC.fight intracellular pathogens.(can lyse body cells!),Cytotoxic CD8 T lympho

10、cytes,Functions of B lymphocytes,B cell antigen receptor-membrane bound antibody moleculeActivated B cells become plasma cells and secrete antibody-potent soluble effector molecues(IgM,IgG,IgA,IgE,IgD)Need T cell help to become activatedExpress class II MHC and can activate CD4+T cells,Functions of

11、B lymphocytes,Where do immune response take place?,Specific lymphocytes need to come into contact with specific pathogen/antigen to make an immune responseThis occurs in the specialised micro-environment of the lymph nodeFigure 8.Structure of a lymph node,Where do pathogens enter the body?,Barriers-

12、skin,nasopharynx,gut,lungs(mucosa)a)recognise pathogenb)make an immune responseThe mucosa contains organised lymphoid tissue(eg peyers patches in the gut)and many lymphocytes,Class exercise,What happens if I vaccinate you?Why do I do this?How does it work?Why is it effectiveWhat happens when you eat

13、 food?What happens to food?Where does it go?Do you make an immune response to food?Why might you have rheumatoid arthritis or multiple sclerosiswhat are the symptoms?what is happening?what is the cause?,So why dont you respond to self antigen?,Tolerance,T and B lymphocytes have unique antigen recept

14、orsThe T cell receptor(TCR)is produced by the genetic organisation germ-line DNAThere are approximately 10 17 different TCRs!During development,TCRs go through 2 selection procedures,Thymic education,Pre-T cell into the thymus:Positive selection:TCR binds to MHC=GROWNegative selection:TCR has high a

15、ffinity for MHC+self peptide=DIEmature T cell,Figure 9,Structure and function of the thymus,What happens if I vaccinate you?,Intentional administration of a harmless or less harmful form of a pathogen to induce a specific immune response that protects the individual against later exposure to the sam

16、e pathogen.Stimulate specific adaptive immune response(antibodies;T cells)Memory,Figures 10,11 and 12,Vaccination protocols,effect on disease prevalence and immune response,What happens when you eat food?,Ingest kilogram quantities of foreign antigenDigest and absorb nutrients etcDo not make an immune response against food(except in disease eg)coeliac disease-respond to glutenThe mucosal immune system functions to switch off responses to ingested/inhaled antigens.,THIS IS ORAL TOLERANCE,Why migh