Lec 3

• Primary lymphoid organs


  Where immune cells develop
• Bone Marrow


  • ALL blood cells start here
  • Hematopoiesis occurs within the bone marrow
  • Blood supply allows for cell migration (especially important in emergency situations)
• Thymus


  • T cells migrate here and mature here
  • Located above and in front of heart
  • Shrinks with age (immune system also fades with age)
  • As you get older you are going to have more memory cells so that body is not going to need to make as many new T cells
• Thymocytes

  Immature T cells
• Secondary lymphoid organs

  Initiation of an immune response
• Secondary lymphoid organs

  • Have antigen presenting cells (macrophage, dendritic cells, B cells) and endothelial cells (Have specific proteins and receptors that draw the cells in)
  • Inside secondary organs, clonal expansion will occur and differentiate into effector cells after lymphocyte is activated
• Lymph nodes & Vessels

  • T and B cells camp out in the nodes and fluid is drained into nodes
  • All fluid HAS to go through here and get checked out (like TSA for lymph)
  • Multiple ways in but only one efferent pathway
  • Antigens travel to lymph nodes (freely or carried by an AB) then get presented to T cells (tcells become activated and are effectors
  • Nodes are perfect meeting spot for antigen and immune cells
  • Chemokines send out "come here" signals (gradients)
  • Lymphatics carry lymph back into blood after (move vla muscle contractions)
• Lymph


  • Comes from blood plasma, interstitial fluid
  • Venules, lymph vessels
  • Contains macrophages, dendritic cells, lymphocytes
• Spleen


  • Filters blood
  • First line of defense against blood-borne pathogens important for systemic pathogens
  • NO LYMPHATICS
  • One way in and out
  • PALS has Bealls follicles and T cells but they are separated (part of white pull
  • Spleen and lymph nodes are highly organized
  • Can't have Bandy cell stored together because they will activate each other and it selbe BAD
• Bone Marrow, thymus


  Primary Lymphoid Organs
• Lymph Nodes and Vessels, Spleen

  Secondary Lymphoid Organs