The immune system

• Anatomical barriers include: Unbroken skin, mucous membrane and ciliary action
• Normal Flora residing in: intestine vagina nasopharynx
• Yeast is a normal Flora in small numbers
• In antibacterial therapy, yeast thrive and invade intestine since ALL bacteria suppressing yeast is killed
• Lysozyme and Lactoferrin are present in sebaceous and sweat secretions
• Lysozyme cleaves cell wall of Gram-positive bacteria
• Lactoferrin binds Iron that is used by bacteria for growth thus inhibiting proliferation
• Pepsin in stomach digests bacterial surface protein
• Ph 1 is the acidity optimal for stomach
• Skin Ph= 5.5-5.6
• Vagina in IS = 5
• Neutrophil is the most effective phagocyte (also dendritic cell)
• Langerhan cells are phagocytes in skin
• Interdigitating dendritic cells are APCs of secondary lymphoid organs and Thymus
• Intersitial dendritic cells are APCs of major organs
• Macrophage in Liver. Kupffer cells
• Macrophage in brain. Microglial cells
• Macrophage in kidney. Mesangial cells
• Macrophage in lungs. Alveolar cells
• Macrophage in bones. Osteoclasts
• Macrophage in spleen. Splenic macrophage or Littoral cells
• Mast cells come from connective tissue that posses same secretory contents such as basophil
• Mast cells contain heparin and histamine
• Nk cells are known to be the most potent type I hypersensitivity initiator
• NK CELLS: attacks virally infected cells and tumor cells and secrete perforin and granzyme
• Nk Cells kills infected cells by 1. ADCC or Antibody dependent cellular cytotoxicity
• Nk Cells kills infected cells by 2. recognition of stress protein in cells in the absence of inhibitory signals such as MHC (Class I)
• Inhibitory receptors:

  1. Killer cell immunoglobulin-like receptor
  2. ILT/LIR
  3. CD94/NKG2A
• Nk Cells are called null lymphocyte since it expresses no CD Marker for T/B cells, only CD16 and CD 56
• NK cells bridge innate and adaptive immune response
• When exposed to IL2 and IFN-y, NK cells are called Lymphocyte Activated Killer cells
• Humoral component of innate

  1. inflammation
  2. Complement
  3. Cytokines
  4. Phagocytes
• ICED: Initiation Chemotaxis Engulfment Digestion
• Chemotaxin: initiates chemotaxis wherein cells move in a certain direction
• Chemotaxin example:

  1. Antibodies
  2. Crp
  3. C5a
• Bacterial peptides can be also a Chemotaxin
• Random motion if there is no chemotaxin
• Boyden chamber is the test for chemotaxis
• If positive chemotaxis means migration towards site, negative chemotaxis means away from site
• Receptors of innate immunity recognize adherence to cells of PAMP: pathogen associated molecular pattern