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Lecture 2

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Michelle French

Lecture 2  What does our immune system do?  Destroy pathogens  Detects and kills abnormal cells  Early cancerous cells  HIV patients whose immune systems are comprised are much more prone to different cancer types than healthy individuals  Remove cell debris from our body  What kinds of pathogens are there?  Both extracellular and intracellular  Parasitic worms  blood, GI tract, eye, malaria protozoan  Fungi  Vaginal yeast infection, throat yeast infection  Protozoa  sleeping sickness in the blood  Bacteria (cells)  inside and outside cells  Can survive and reproduce outside the host  Most bacteria are killed by drugs known as antibiotics  Viruses (not cells)  Require host cells to replicate  DNA or RNA based and can be either double stranded or single stranded  Coated by their own encoded proteins and in certain cases an extra envelope layer budding off from the host membrane with embedded glycoproteins that have attachment specificity (e.g. influenza binds epithelial cells lining the respiratory tract)  Viruses cannot be killed via antibiotics, certain viruses can be treated with antiviral drugs  How do we defend against pathogens?  Physical Barriers  skin, mucous, acid, lysosome (on tears, helps break down bacteria cell wall)  Prevent pathogens from entering interstitial compartments  If the first line of defense fails, then the internal immune response takes over (Innate, Adaptive)  Non-specific Innate immunity  rapid, non-specific  Begins within minutes to hours  Mast cells, neutrophils, basophils, eosinophils, mast cells  Specific Acquired immunity  lymphocytes, specific  Acquired immunity can be divided into cell mediated immunity and humoral immunity  Cells specific for antigen  B cells, T cells, NK cells  What are the components of the immune system  Primary lymphoid tissue . Bone Marrow, Thymus  Secondary lymphoid tissue   Encapsulated  spleen, lymph nodes (from the lymphatic system),  Unencapsulatethe (diffuse lymphoid tissue)  gut associated lymphoid tissue (GALT, Peyers Patch  M cells), mucosal associate lymphoid tissue (MALT), Tonsils  Lymphatics  Return excess tissue fluid to the blood  Transport pathogens/dendritic cells to lymph nodes  Transport fat from digestive system to the blood  GALT  Specialized lymphoid organs  Lymph nodes  monitor lymph  Spleen  monitor blood (red pulp), no lymphatics  Both contain mature immune cells that interact with pathogens presented by APC and initiate and immune response  Immune cells found in blood, lymph and tissues  Lymphocytes  B lymphocytes, T lymphocytes, NK cells  Monocytes  macrophages  Neutrophils  Basophils  Eosinophils  Innate Immune System  Phagocytes  Neutrophils (50%-70% WBC, release cytokines and cause fever and inflammation)  Monocytes  Macrophages, Dendritic cells (APC)  An infection can cause endothelial cells of a neighbor capillary to up regulate adhesion molecules. This will cause the rolling effect and slowing down of circulating white blood cells on the capillaries endothelium leading to diapedesis (entering the tissue). By means of chemotaxis they will move towards the infected area where they will initiate innate immunity (phagocytose).  Chemotaxin  bacterial toxins, product of tissue injury, cytokines  Phagocytosis of pathogens  Using Toll receptor on the surface of their membrane, macrophages can bind bacteria leading to engulfing and phagocytosis  Opsonization  in the acquired immune system, antibodies specific to the pathogens will bind epitopes and coat the pathogen. The macrophages will in turn bind the Fc region of the antib
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