IMMUNITY = Ability of organism to resist infection --- by means of

1. IMMUNITY = Ability of organism to resist infection --- by means of interactions of a variety of cells and cell products 1. Nonspecific (innate): Phagocytes: (1) engulf, (2) digest and (3) destroy bacteria in lysosomes, (4) present antigens and (5) attract cells of Specific immunity 2. Specific (adaptive) (1) Cell-mediated: Cell TCdegranulationapoptosis APC TH1cytokinesinflamation (2) Humoral (antigen-antibody mediated) APC TH2interleukins Bplasma Ig memorycells APC=Antigen Presenting Cell

2. The innate immune response is mediated by phagocytes. • Phagocytes recognize pathogen-associated molecular patterns (PAMPs) via a family of membrane-bound pattern-recognition molecules, or PRMs. • Interaction of the PAMPs with PRMs activates phagocytes to produce metabolic products that kill the pathogen or limit its effects. • Many pathogens have developed mechanisms to inhibit phagocytes.

3. Phagocyte armor 2. Bactericides: H-peroxide Superoxide Hydroxyl radical Singlet oxygen 1. Enzymes: Lysozyme Protease Phosphatase Lipase Nuclease 3. Aerobic/Anaerobic switch 4. APC – system (antigen-presenting cells)

4. Nonspecific phagocytes present antigen to Specific T cells, triggering the production of effector T cells and antibodies. • Immune T cells and antibodies react directly or indirectly to neutralize or destroy the antigen.

5. Inflammation is characterized bypain,swelling(edema), redness(erythema),andheat. The inflammatory response is a normal and generally desirable outcome of an immune response. Uncontrolled systemic inflammation, called septicshock, can lead to serious illness and death.

6. The adaptive immune response is characterized by specificity for the antigen, • The ability to respond more vigorously when re-exposed to the same antigen i.e.memory, and • The ability to discriminate self antigens from nonself antigens, i.e. tolerance.

7. Specificity • Memory • Tolerance

8. Immunogens are foreign macromolecules that induce an immune response. Molecular size, complexity, and physical form are intrinsic properties of immunogens. When foreign immunogens are introduced into a host in an appropriate dose and route, they initiate an immune response. • Antigens are molecules recognized by antibodies or T-Cell-Receptors or TCRs. Antibodies recognize conformational determinants; TCRs recognize linear peptide determinants.

9. T cells recognize antigens presented by APCs or by pathogen-infected cells. At the molecular level, TCRs bind peptide antigens presented by MHC proteins. These molecular interactions stimulate T cells to kill antigen-bearing cells or to produce cell-stimulating proteins known as cytokines.

10. IMMUNITY 1. Nonspecific: phagocytosis & destruction in lysosomes PMN, Monocytes (circulate) Macrophages (fixed to tissue) 2. Specific a) Cell-mediated: Cell TC degranulation apoptosis APC TH1 cytokines inflamation b) Humoral (antigen-antibody mediated) APC TH2interleukins Bplasma Ig memory c) APC cells are Macrophages, Dendritic cells, B-cells

11. TH1 and TH2 cells play pivotal roles in cell-mediated and antibody- mediated immune responses. TH1 inflammatory and TH2 helper cells each stimulate effector cells through the action of cytokines.

12. T-cytotoxic (TC )cells recognize antigens on virus-infected host cells and tumor cells through antigen-specific TCRs. • Antigen-specific recognition triggers killing via perforin and granzymes. • Natural killer (NK) cells use the same effectors to kill virus-infected cells and tumors. However, NK cells do not require stimulation, nor do they exhibit memory. NK cells respond in the absence of MHC proteins.

13. Ig (antibody) proteins consist of four chains, two heavy and two light. The antigen-binding site is formed by the interaction of variable regions of heavy and light chains. Each class of Ig has different structural and functional characteristics.

14. Opsonization The complement system catalyzes bacterial cell destruction and opsonization. Complement is triggered by antibody interactions or by interactions with nonspecific activators. Complement is a critical component of both innate and adaptive host defense.

15. The antigen-binding site of an Ig is composed of the V (variable) domains of one heavy chain and one light chain. Each heavy and light chain contains three complementarity-determining regions, or CDRs, that are folded together to form the antigen-binding site.

16. Recombination allows shuffling of various pieces of the final Ig genes. Random reassortment of the heavy- and light-chain genes maximizes genetically encoded diversity. Imprecise joining of VDJ and VJ segments as well as hypermutation and affinity maturation also contribute to virtually unlimited immunoglobulin diversity.

17. Antibody production is initiated by antigen contact with an antigen-specific B cell that processes the antigen and presents it to an antigen-specific TH2 cell. • The activated TH2 cell then signals the antigen-specific B cell to produce antibody. • Activated B cells live for years as memory cells and can rapidly produce large quantities (high titers) of antibodies upon re-exposure to antigen.

18. The thymus is a primary lymphoid organ that provides an environment for the maturation of antigen-reactive T cells. • Immature T cells that do not interact with MHC protein (positive selection) or react strongly with self antigens (negative selection) are eliminated by clonal deletion in the thymus.

19. T cells that survive positive and negative selection leave the thymus and can participate in an effective immune response. • B cell reactivity to self antigens is controlled through clonal deletion, selection, and anergy.

20. Cytokines are soluble mediators produced by leukocytes that regulate interactions between cells. Several cytokines such as IL-1, IL-2, and IL-4 affect leukocytes and are critical components in the generation of specific immune responses. Other cytokines such as IFN and TNF affect a wide variety of cell types. Chemokines are produced by a variety of cell types in response to injury and are potent attractants for nonspecific inflammatory cells and T cells. (IL stands for Interleukin)

21. Cytokines – small soluble regulatory proteins Lymphokines – cytokines produced by lymphocytes Interleukins – interleucocyte regulation IL1 Macrophages to TH  activation IL2 TH2 to TH2 autocrene proliferation IL3 TH1 to stem cells IL4 TH2 to B  proliferation plasma cells IgG, E IL5 TH2 to B  proliferation plasma cells lgA IL8 Leukocytes chemoattracts T-cells & PMNs IL10 TH2 to TH1 inhibition IL12 Macrophages to TH1  activation Chemokines IFN – InterFeroNs leukocytes  tissue cells – antiviral TGF – T-cell Growth Factor TNF – Tumor Necrosis Factor MCP – Macrophage Chemoattractant Protein

22. Immunization Agammaglobulinemia Natural Artificial Active Passive Immunization (vaccination) Receives antibodies Exposure Receives immunogens • Active: Immunogens Passive: antiserum (antitoxin) • Killed pathogens (formaldehyde) Antibodies in serum • Attenuated strains of pathogens Hyperimmune persons • Toxoids Pooled Immunoglobulins • Synthetic epitope peptide; • Recombinant vector vaccine: Viral genes cloned in E. coli • Cloned genes injected and expressed (tumor-specific antigen)

23. Hypersensitivity - type I Immediate hypersensitivity Allergy, asthma, anaphylaxis Hypersensitivity - type II Organ-specific Autoimmune diseases Autoantibodies: Hashimoto’s disease against thyroid gland Juvenile diabetes against Langerhans islets Hypersensitivity - type III SystemicAutoimmune diseases Systemic lupus erythematosis (SLE) Hypersensitivity - type IV Delayed hypersensitivity Contact dermatitis, tuberculin test

24. Immunity to infectious disease can be either passive or active, natural or artificial. • Immunization, a form of artificial active immunity, is widely employed to prevent infectious diseases. • Most agents used for immunization are either attenuated or inactivated pathogens or inactivated forms of natural microbial products.

25. Hypersensitivity results when foreign antigens induce cellular or antibody immune responses, leading to host tissue damage. Autoimmunity occurs when the immune response is directed against self-antigens, resulting in host tissue damage.

26. Hypersensitivity - type I Immediate hypersensitivity Allergy, asthma, anaphylaxis Hypersensitivity - type II Organ-specific Autoimmune diseases Autoantibodies: Hashimoto’s disease against thyroid gland Juvenile diabetes against Langerhans islets Hypersensitivity - type III SystemicAutoimmune diseases Systemic lupus erythematosis (SLE) Hypersensitivity - type IV Delayed hypersensitivity Contact dermatitis, tuberculin test

27. T-cell Cytotoxic Attack

28. B-cell Antibody Attack T-cell

29. Complement alternatives

30. Mimicry (Rabies, Rhino, Vaccinia)

31. Hiding the binding site (Polyo, Influenza, HIV)

32. Epitope cover-up (wolf in sheep’s skin – E. coli)

33. Hiding in the police Department (Shigella, Mycobacterium, Chlamydia)

34. Clinical methods • Culture diagnostic: • Blood , Bacteremia -> Septicemia -> Septic shock • Urine , Bacteriuria – bacteria in urin • Feces, Salmonella, Shigella • Antibiogram • Serodiagnostic • Antibody titer • Polyclonal antibodies • Monoclonal antibodies

35. Safety in the clinical laboratory requires effective training, planning, and care to prevent the infection of laboratory workers with pathogens. Materials such as live cultures, inoculated culture media, used hypodermic needles, and patient specimens require specific precautions for safe handling.

36. Proper sampling and culture of the suspected pathogen is the most reliable way to identify an organism that causes a disease. The selection of appropriate sampling and culture conditions requires knowledge of bacterial ecology, physiology, and nutrition.

37. Antimicrobial drugs are widely used for the treatment of infectious diseases. Pathogens should be tested for susceptibility to individual antibiotics to ensure appropriate chemotherapy. This rigorous approach to antimicrobial drug treatment is usually applied only in health care settings.

38. An immune response is a natural outcome of infection. Specific immune responses, particularly antibody titers and skin tests, can be monitored to provide information concerning past infections, current infections, and convalescence.

39. Polyclonal and Monoclonal antibodies are used for research and clinical applications. Hybridoma technology provides reproducible, monospecific antibodies for a wide range of clinical, diagnostic, and research purposes.

40. Antigen–antibody reactions require that antibody bind to antigen. Specificity and sensitivity define the accuracy of individual serological tests. Neutralization and precipitation reactions are examples of antigen-binding tests that produce visible results involving antigen–antibody interactions. • In serological reactions, high specificity prevents false-positive reactions. High sensitivity prevents false-negative reactions.

41. Specificity: binding with a single antigen (positive + negative controls no false +) Sensitivity: lowest amount of antigen dedectable (no false -) ______________________________________ Precipitation soluble - soluble Agglutination (100 x precipitation sensitive) surface bound - soluble

42. Direct agglutination tests are widely used for determination of blood types. A number of passive agglutination tests are available for identification of a variety of pathogens and pathogen-related products. Agglutination tests are rapid, relatively sensitive, highly specific, simple to perform, and inexpensive.

43. Fluorescent antibodies are used for quick, accurate identification of pathogens and other antigenic substances in tissue samples and other complex environments. Fluorescent antibody-based methods can be used for identification, quantitative enumeration, and sorting of a variety of cell types.

44. EIA (ELISA) and RIA methods are the most sensitive immunoassay techniques. Both involve linking a detection system, either an enzyme or a radioactive molecule, to an antibody or antigen, significantly enhancing sensitivity. ELISA and RIA are used for clinical and research work; tests have been designed to detect either antibody or antigen in many applications. For more specificity apply IMMUNOBLOT

45. Immunoblot procedures are used to detect antibodies to specific antigens or to detect the presence of the antigens themselves. The antigens are separated by electrophoresis, transferred (blotted) to a membrane, and exposed to antibody. Immune complexes are visualized with enzyme-labeled or radioactive secondary antibodies. Immunoblots are extremely specific, but procedures are complex and time-consuming.

46. Nucleic acid hybridization is a powerful laboratory tool used for identification of microorganisms. A nucleic acid sequence specific for the microorganism of interest must be available in order to design a probe. Perhaps the most widespread use of probe-based technology is in the application of gene amplification (PCR) methods. Various DNA-based methodologies are currently used in clinical, food, and research laboratories.

47. Virus propagation in vitro can be accomplished only in tissue culture. Therefore, most diagnostic techniques for viral identification are not growth-dependent, but routinely rely on immunoassays and nucleic acid-based techniques. Electron microscopy techniques are useful for direct observation of viruses in host samples.

48. Epidemiology The study of disease in populations. To understand infectious disease, the epidemiologist studies the interactions of the pathogen with the host population. It is a population level ecology

49. Concepts of Epidemiology Prevalence: % of diseased Incidence: # of diseased Endemic - Epidemic - Pandemic Mortality - Morbidity Infection – Incubation - Acute period – Decline - Convalescence Emerging Infectious Diseases

50. Transmissions: • Reservoirs - Vectors - Carriers Public Health Measures • Surveillance - Reservoir control - Transmission control - • Immunization - Quarantine - Pathogen eradication