Tissues of the immune system

• What are the primary lymphoid organs?


  Where cells are made-

  Bone marrow - develop mature B cells and foetal liver- heamtopoesis
• What is the function of primary lymphoid organs?


  Where immune cells are made
• What is the role of the bone marrow?

  Develop mature B cells
• What does the foetal liver do?

  Haematopoiesis
• What are secondary lymphoid organs responsible for?

  Where immune response takes place
• Name a secondary lymphoid organ.

  Spleen, lymph node and MALT
• What is the function of the spleen?

  Filters blood
• What does MALT stand for?

  Mucosal associated lymphoid tissue
• Where is MALT found?

  Gastrointestinal, respiratory, urogenital tracts
• Where are mature B cells developed?

  In the bone marrow
• What antibody classes do mature B cells express?

  IgM and IgD
• What happens to mature B cells after development?

  They exit bone marrow and enter circulation
• What triggers B cells to become activated?

  Encountering their antigen
• What do activated B cells produce?


  Plasma and memory cells
• What is the function of the lymphatic system?

  Transport immune cells and foreign particles
• What fluid is transported through the lymphatic system?

  Lymph
• Where are immature T cells made?


  Cortex of the thymus
• Where are mature T cells found in the thymus?


  Medulla of the thymus
• What types of T cells are specialized in the thymus?

  CD4 and CD8 T cells
• What happens if there is no thymus?

  No T cells will be produced
• How do the functions of B cells and T cells differ?

  B cells produce antibodies; T cells eliminate infections
• Generation of mature B cell -steps


  B cell receptors generated in Bon marrow, B cell precursor rearranges its immunoglobulin genes,

  • immature B cell bound to antigen is removed from the repertoire- negative selection
  • Mature B cells bound to foreign antigen activated and B cells migrate to the peripheral lymphoid organs
  • Activated B cells give rise to plasma cells and memory cells.
• Bone marrow

  • mesh fibroblast network to provide environment for stem cells to differentiate into WBC.
  • Development of RBC start with nucleus and later removal by macrophages
• during infection soluble factors produced- cytokines


  when you have an infection you have a high level of pro inflammatory factors - WBCs then travel to the site of infection
• Lymph node diagram

  
• Lymph node function

  lymph nodes contain specialised comprtments where immune cells and WBCs congregate until an immune response is triggered.
• Lymph node histology

  
• Dendritic cells and lymph nodes during an infection

  • DCs take up antigen and enter lymph node then macrophages and T cells interact with WBCs to produce immune response.
  • T helper cells then make B cells differentiate into plasma cells to then produce antibodies. these will then leave the node from the afferent vessel and go to the site of infection.
  • the activated T cell and b cells can also migrate to site of infection to further produce an immune response
• diffuse lymphatic tissue

  situated around the body -respiratory passage, alimentary canal, ocular surface and urogenital trac
• lymph node gut associated lymphoid tissues (GAIT)

  • tonsils
  • colon
  • adenoids
  • appendix
  • peyers patches
• payer patches


  • the bulk of tissue is B cells with T cells occupying areas between follicles.
  • the antigen enters across a specialised epithelium made up of M cells - give antigens to lymphoid strructues and if necessary make an immune response by producing antibodies which will migrate from node and stay on surface of gut lumen.
• the spleen red pulp vs white pulp


  • red pulp- red blood cells present here- removes waste from blood or gets rid of damaged blood cells.- in some animals it acts as a storage for RBCs used in times of extreme exercise- seen in horses
  • white pulp- where lymphocyte responses to blood borne pathogens are made
• lymphocyte re circulation

  • circulation is very important as you have phagocytic cells and WBCs- circulating into other areas.
  • if cells can’t recirculate or if they fail to migrate into other cells you can get particular diseases
  • lymphocyte in mature animals move through the circulation and the lymphatic duct between various organs

  
• organisation of the lymphoid tissues of the spleen 


  draw this / cover and label

  
• Lymphatic system - know where spleen , peyers patches, thymus are and bone marrow 


  Label them