Immunology I

Immunology I

1. the study of the body's defence mechanisms

2. immune responses

   • Specific
     • required several days
     • daptive
     • Cell-mediated
     • involve lymphocytes
       • Cell-Mediated immunity
         • T-lymphocytes
           • originally from red bone marrow
             • perinatal migration & stop off in thymus gland
               • of or relating to the time, usually a number of weeks, immediately before and after birth.
               • confers immunological competence on T-cells
               • most stored in inactive state
                 • as small lymphocytes
           • less than 10% of cells r selected
           • the only with receptors
             • bind to specific antigen
           • activation
             • 1 in 10000 T-cells may respond
               • become activated/sensitized cells
                 • 1. increase size
                   • 2. divides mitotically
                     • 3. form clone of cells
                       • 4. produce variety of specialised cells (T-cell subsets)
                         • Cytotoxic T-cells
                           • combine with surface antigens releasing Cytokines
                             • e.g. perforine-1
                               • membrane pores
                                 • i.e destroy infected cells
                         • Helper T-cells
                           • release interleukins --> infection site
                             • attract macrophages
                             • make other lymphocytes competent to help
                         • memory cells
                           • cause rapid second response
                             • the first response take from 3-14 days
                           • bearing receptors to the antigen
                             • pathogens destroyed before it can get established
                               • e.g. Measles & chickenpox
                             • cold/influenza viruses change their surface antigens
                         • suppressor T-cells
                         • 5. T-cells leave lymph nodes to infection site
             • helper T-cells secret cytokines
               • help activate T-cells
         • antigen-presenting cells (APCs)
           • dendritic cells
           • engulf foreign antigen
           • macrophages
             • phagocytoses pathogen
               • break down surface antigens
             • e.g antigen-MHC complex
         • competent lymphocytes;
       • Antibody-Mediated immunity
   • non-specific
     • innate
     • types
       • 1. physical barrier
         • the skin
           • sweat and sebum
             • destroy some bacteria
               • defensins
               • mucin
               • lysosome
         • the stomach
           • acid secretions
             • destroy microorganisms
         • the lungs
           • sticky mucous
             • lining in Bronchi andbronchioles
       • 2. Cytokines (soluble molecules)
         • the special proteins that are secreted collectively when pathogens enter tissues
         • interferons
           • inhibit viral macromolecule production
           • stimulate other immune responses
           • release in viral infections
         • Interleukins
           • secreted by macrophages and lymphocytes
           • regulate interaction between various parts of the immune system
           • Functions with Tumor Necrosis Factor TNF in mediating inflammation
         • some of them stimulate NK cell activation
           • Natural Killer Cells (NK)
             • large granular lymphocytes from the bone marrow
             • 15% of the circulating lymphocytes
             • release cytokines e.g perforine
               • cause pores in PM of target cells
                 • PM= Plasma Membrane
               • Granzymes then activate a cascade of reactions
                 • cause apoptosis
       • 3. inflammation
         • cells release histamine & serotonine
           • dilate blood vessels in the infected area
             • increase capillary wall permeability
               • cause Oedema
             • brings monocytes + neutrophils+ plasma protein gamma globulins (antibodies)
               • releasing endogenous pyrogens
                 • interleukin-1
                 • prostaglandins
                 • reset body's thermostat in the hypothalamus to higher (T)
                   • produce fever or pyrexia
                     • effects directly bacterial metabolism
       • phagocytosis
         • major function of inflammation
         • they're leucocytes
           • Monocytes
             • 1. leave the circulation
               • 2. transform into macrophages
                 • phagocytose 〰100 bacteria before dying!
           • Neutrophils
             • phagocytose 〰 20 bacteria before dying
               • dead neutrophils formed pus
             • smaller
         • some bacteria resist it
           • e.g. tuberculosis bacilli
         • distributed widley
           • particularly in the gut wall & lungs
         • release interleukin-1
           • as inflammatory process
     • prevent the spread of infection
       • until specific come into play

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