Adaptive Immunity

• What is the primary function of the immune system?

  To recognize, remember, and respond to specific antigens.
• How does the adaptive immune system remember prior exposures?

  It is characterized by specificity for each pathogen and retains immunologic memory.
• What is the outcome of the adaptive immune response?

  It can eliminate microorganisms and lead to recovery from disease.
• What advantage does immunologic memory provide during reinfection?

  It allows the host to respond more effectively to reinfection with the same microorganism.
• What are the main components of the adaptive immune system?

  • Cellular components: T lymphocytes, B lymphocytes, Plasma Cells
  • Humoral components: Antibodies, Cytokines
• What percentage of circulating white blood cells do lymphocytes represent?

  Between 20% to 40% of circulating WBC.
• What is the size of lymphocytes compared to red blood cells?

  Lymphocytes are 7 to 10µm in diameter, almost the same as RBCs.
• What are the three major populations of lymphocytes?

  T Lymphocytes, B Lymphocytes, and NK Cells.
• What are the primary lymphoid organs in humans?

  The bone marrow and the thymus.
• What are the secondary lymphoid organs?

  The spleen, lymph nodes, appendix, tonsils, and mucosal associated lymphoid tissue.
• What is the function of primary lymphoid organs?

  • Maturation site of lymphocytes
  • Bone marrow: maturation of B cells
  • Thymus: maturation of T cells
• What is the average weight of the adult human bone marrow?

  1300 to 1500g.
• What is the main source of hematopoietic stem cells?

  The bone marrow.
• What is the role of thymosin in the thymus?

  It stimulates T cell maturation.
• Where is the thymus located in the human body?

  In the thorax, below the thyroid gland and overlying the heart.
• How does the weight of the thymus change from birth to puberty?

  It weighs about 30g at birth, reaches 35g at puberty, and then gradually atrophies.
• What are the main parts of the thymus?

  • Cortex: contains thymocytes (immature T cells)
  • Medulla: contains mature T cells
• How long does the maturation of T cells take in the thymus?

  Approximately 3 weeks.
• What percentage of cortical cells die in the thymus before maturing into T cells?

  Approximately 97%.
• What is the role of secondary lymphoid organs?

  • Activation sites for lymphocytes
  • Lymphopoiesis occurs dependent on antigenic stimulation
• What is the largest secondary lymphoid organ?

  The spleen.
• What is the function of the spleen in the immune system?

  It acts as a lymphatic filter and is an important site of antibody production.
• What is the approximate size and weight of the adult spleen?

  About 12cm and weighing 150g.
• Where is the spleen located in the body?

  In the upper left quadrant of the abdomen, just below the diaphragm.
• What are the two main types of splenic tissue?

  Red pulp and white pulp.
• What is the function of red pulp in the spleen?

  It destroys old red blood cells.
• What is the function of white pulp in the spleen?

  It contains lymphoid tissue and is involved in immune responses.
• Where are T cells located in the spleen?

  Near the central arteriole in the white pulp.
• Where are naïve B cells located in the spleen?

  In the primary follicles of the white pulp.
• Where are activated B cells found in the spleen?

  In the secondary follicles of the white pulp.
• What is the function of lymph nodes in the lymphatic system?

  They act as a lymphoid filter and central collecting points for lymph fluid.
• What are the three main regions of a lymph node?

  Cortex, paracortex, and medulla.
• What is found in the cortex of lymph nodes?

  B cell area.
• What is found in the paracortex of lymph nodes?

  T cell area.
• What is found in the medulla of lymph nodes?

  Differentiated cells and antigen presenting cells (APCs).
• What are the types of Mucosal-Associated Lymphoid Tissue (MALT)?

  • BALT: Bronchus Associated Lymphoid Tissue
  • GALT: Gut Associated Lymphoid Tissue
  • CALT: Cutaneous Associated Lymphoid Tissue
• What is the role of BALT?

  It is associated with IgA production in response to inhaled antigens.
• What is the role of GALT?

  It is important for the development of tolerance to ingested antigens.
• What is the role of CALT?

  It interacts with lymphocytes in the skin.
• What are clusters of differentiation (CD)?

  They standardize names of membrane proteins found on human white blood cells.