Immunology part 2

• Secondary Lymphoid Organs

  Have two major functions:

   Trap & concentrate foreign substances

   Main sites of production of antibody and activation of antigen-specific T cells
• Organs include:

   Lymph Node

   Spleen

  MALT
• Lymph nodes

  -Filter lymph (which drain antigens from the tissues)

  -Found at the junctions of some of the lymphatic vessels.
• Cortex (outer layer) - These germinal centers are the sites of B cell development and maturation into plasma cells.
• Paracortex (middle layer) - Antigen-presenting-cell (APC) such as dendritic cells work to present antigen to the T cells and activate them.
• Medulla (inner part) - Lymph from the outside enters at several sites surrounding the cortex and filters toward the medulla, where it exits the lymph node.
• Spleen

  Main function is to filter blood.
• White pulp

  -Associated with immune function. It contains primarily T cells
• Red pulp

  -Associated with the removal of aged erythocytes & platelets Contains macrophages which can engulf and digest them
• Marginal zone

  -Separates the white pulp and the red pulp

  Contains lymphoid follicles; lots of B cells are present
• Mucosal-Associated Lymphoid Tissue

  • Lymphoid tissue lines the mucous membranes associated with the gastrointestinal tract, thyroid, breast, lung, salivary glands, eye, and skin
• Lymphokines are Cytokines produced by T lymphphocytes
• Monokines are produced by monoclear phagocytes
• Examples of cytokines:

  Interferons (IFN)

  Interleukins (IL)

  Colony Stimulating Factor (CSF)
• Interferons(IFN)

   A group of immunoregulatory cytokines produced very early during viral infections.
• IFN a and IFN b is produced by virus-infected cells.
• IFN g is released by T lymphocytes and NK cells.
• Most interleukins are made by T cells
• Colony Stimulating Factors govern the formation, differentiation and function of hematopoietic cells and are made by monocytes and macrophages
• Cytokines works via complement system
• Complement system is a group of plasma protein mediators that can act as an innate nonspecific defense
• the complement system causes the lysis of foreign and infected cells, the phagocytosis of foreign particles and cell debris, and the inflammation of surrounding tissue.