Cells & Organs of the immune system Dr. Mohed. Shaker
Cells involved in immunity platelets eosinophil megakaryocyte T Lymphocyte Pluripotent hematopoietic stem cell neutrophil B Lymphocyte common lymphoid progenitor basophil common myeloid progenitor Study Guide Can you describe the major classes of cells involved in immunity? Which cells are considered mononuclear leukocytes? What is the relationship between the monocyte and the macrophage? What is the relationship between the B-cell and the plasma cell? plasma cell mast cell Natural Killer cell monocyte macrophage
Polymorphonuclear leukocytes (or Granulocytes) Where is that stuff? Blood Serum or Plasma Leukocytes, Platelets and RBC Mononuclear Cells Polymorphonuclear leukocytes (or Granulocytes) Serum Proteins Immunoglobulins Complement Clotting factors Many others Lymphocytes (T cells, B cells & NK cells) Monocytes Neutrophils Eosinophils Basophils
Lymphoid Organs Primary or central lymphoid organs bone marrow and thymus where lymphocytes are generated Secondary or peripheral lymphoid organs where adaptive immune responses are initiated
Distribution of Lymphoid Tissues
Response to Initial Infection
Stages of Response to Infection
Course of Typical Acute Infection
Immune Cells and Innate Immunity Phagocytes Neutrophils Moncyte/macrophage Eosinophils (to a lesser extent) NK cells (large granular lymphocytes) Antibody-dependent cell-mediated cytotoxicity (ADCC) Have two major functions Lysis of target cells Production of cytokines (IFN-g and TNF-a) Act against intracellular pathogens Herpesviruses Leishmania Listeria monocytogenes Act against protozoa Toxoplasma Trypanasoma
Immune Cells and Innate Immunity (cont’d) g/d T cells Two types of T cell receptors One composed of a and b chains (basic T cell antigen receptor) One composed of g and d chains (minor population of T cells) Two groups of g/d T cells One group found in lymphoid tissues One group located in paracellular space between epithelial cells Recognizes unprocessed target antigen in absence of APC help B-1 cells (minor fraction of B cells, do not require T-cell help) Mast cells Located in serosa, under epithelial surfaces and adjacent to blood vessels, nerves and glands Capable of phagocytosis Process and present antigen using MHC class I or II receptors LPS can directly induce release of mast cell mediators Complement (C3a and C5a) induce mast cells to release mediators Chemotaxis, complement activation, inflammation TNF-a secreted by mast cells results in neutrophil influx into infected site
Summary of Innate Immunity External and mechanical barriers Receptors for pathogen motifs Soluble antimicrobial proteins Pattern of cytokines produced influences adaptive response