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Lymphatic/Immune System(Britane Olvera, Per.2) - Coggle Diagram

- - - - Constitutes first and second lines of defense
        
        First line of defense: external body membranes (skin and mucosae)
        
        Second line of defense: antimicrobial proteins, phagocytes, and other cells (inhibit spread of invaders; inflammation most important mechanism)
    - - Third line of defense attacks particular foreign substances (takes longer to react than innate)
- - - - Acid: acidity of skin and some mucous secretions inhibits growth; called acid mantle
      - Enzymes: lysozyme of saliva, respiratory mucus, and lacrimal fluid kills many microorganisms; enzymes in stomach kill many microorganisms
      - Mucin: sticky mucus that lines digestive and respiratory tract traps microorganisms
    - - Physical barrier to most microorganisms
      - Keratin is resistant to weak acids and bases, bacterial enzymes, and toxins
      - Mucosae provide similar mechanical barriers
  - - - Phagocytes
      - Natural killer (NK) cells
      - Inflammatory response (macrophages, mast cells, WBCs, and inflammatory chemicals)
      - Antimicrobial proteins (interferons and complement proteins)
      - Fever
- - - - Antibodies, produced by lymphocytes, circulate freely in body fluids
      - Bind temporarily to target cell
        
        Mark for destruction
    - - Lymphocytes act against target cell
        
        Directly—by killing infected cells
        
        Indirectly—by releasing chemicals that enhance inflammatory response; or activating other lymphocytes or macrophages
- - - - Can be a complete antigen or hapten (incomplete)
      - Contain antigentic determinants
      - Can be a self-antigen
    - - All cells are covered with variety of proteins located on surface that are not antigenic to self,
      - MHC proteins
        
        Coded by genes of major histocompatibility complex (MHC) and unique to each individual
        
        Contain groove that can hold piece of self-antigen or foreign antigen
        
        T lymphocytes can recognize only antigens that are presented on MHC proteins
  - - - Origin: both lymphocytes originate in red bone marrow
      - Maturation
        
        Lymphocytes are “educated” in a 2-3 day process and mature in primary lymphoid organs (B cells in bone marrow and thymus)
        
        Lymphocytes are educated for 2 reasons:
        
        Immunocompetence: lymphocytes must be able to recognize only 1 specific antigen.
        
        B or T cells display only one unique type of antigen receptor on
        surface when mature so bind only one specific antigen
        
        Self-tolerance: lymphocytes must be unresponsive to own antigens
      - Seeding secondary lymphoid organs and circulation
        
        Immunocompetent B and T cells not yet exposed to antigen are called naive
        
        Exported from primary lymphoid organs (bone marrow and thymus) to “seed”
        (colonize) secondary lymphoid organs (lymph nodes, spleen, etc.)
        
        Increases chance of encounter with antigen
      - Antigen encounter and activation
        
        Naive lymphocyte’s first encounter with antigen triggers lymphocyte to develop further
        
        Lymphocyte is selected to differentiate into active cell by binding to its
        specific antigen
        
        Referred to as clonal selection
        
        If correct signals are present, lymphocyte will complete its differentiation
        into active cell
      - Proliferation and differentiation
        
        Once selected and activated, lymphocyte proliferates
        
        Forms army of exact copies of itself
        
        Referred to as clones
        
        Most clones become effector cells that fight infections
        
        A few remain as memory cells
        
        Able to respond to same antigen more quickly second time it is
        encountered
        
        B and T memory cells and effector T cells circulate continuously
    - - Genes, not antigens, determine which foreign substances the immune system will recognize
      - Huge variety of receptors: gene segments are shuffled around, resulting in many
        combinations
    - - T cells mature in thymus under negative and positive selection pressures
  - - - Overall T- or Y-shaped antibody monomer consists of four looping polypeptide chains linked by disulfide bonds
      - Four chains consist of:
        
        Two identical heavy (H) chains with hinge region at “middles”
        
        Two identical light (L) chains
    - - Neutralization
      - Agglutination
      - Precipitation
      - Complement fixation
- - - - Protection immediate but ends when antibodies naturally degrade in body