Anatomy Of The Immune System

Anatomy of the Immune System Hematopoiesis Hematopoiesis and Hematopoietic Stem Cells Hematopoiesis: the formation and differentiation of erythrocytes (red blood cells), leukocytes (white blood cells), and thrombocytes (platelets) from hematopoietic stem cells (HSC) Immune cells are all blood cells 2 criteria for stem cells: Self-renewal Differentiation into diverse cell types BUT as stem cells became more and more differentiated, they can begin to use their ability to renew! meaning that the more differentiated it becomes, the less likely it will be to start over as something new! pluripotent: can give rise to virtually any stem type (embryonic stem cells) multipotent: only give rise to cell types of certain tissue (adult stem cell) Leukocyte Lineage Hematopoietic Stem Cells Common Myeloid Progenitor (CMP) Common Lymphoid Progenitor (CLP) Granulocyte Monocyte Erythrocyte Megakaryocyte Lymphocyte lymphoid cells are mostly adaptive T-cells mature in the thymus B-cells mature in the bone marrow natural killer cells myeloid cells are mostly innate exception to the rule: lymphoid origin BUT innate immunity! platelets - keep blood from clotting P Myeloid Cells Granulocytes: Neutrophils, Eosinophils, Basophils, Mast Cells Contain multi-lobed nuclei Lock granular Betise the name Monocyte: Constantly patrolling around Respond very quickly to infection Only called 'monocyte' in the blood Called 'macrophages' when it enters the tissues Inflammatory monocytes: respond quickly to infection Since they enter tissue, they become macrophages and stop infection by Ingesting bacteria/other material Macrophage: Important immune activities: phagocytosis Antigen presentation Cytokine/chemokine secretion Tissue specific macrophages: not formed by HSC formed by the tissue they reside in Dendritic cells: Help us link the innate and adaptive immune system Important in antigen capture and antigen presentation Boosts immune response by showing antigens on its surface To other cells Erythrocyte (red blood cell) Primary function is gas exchange carrying oxygen Some immune activity: Antibody receptors (Fc receptors) Nitric oxide production. Grown to aid in immune response Megakaryocytes: Cells that generate platelets Platelets are called thrombocytes. No known immune activity HOWEVER they are important in blood clot formation Crucial way to sequester infection and keep it localized Contain nuclei BUT platelets do not Lymphoid Cells: all lymphocytes originate in the bone marrow B-cells mature in bone marrow Thymus T-cels mature in thymus -principle cell involved in adaptive immunity Bone marrow -constant migration within blood circulation e all times -have very specific receptors BUT those receptors are generated of random -morphologically identical small, round cells w/ latge naciei basic nomenclature: mature B and T cells that are Fully formed naire: mature & and T cells that have not yet encountered an antigen once they encounter an anligen and become activated, they con become effector/memory cells effector cells: cells with specific functions to deal w/ pathogens a part of the primary response memory cells: cells that do not engage antigen upon initial encounter BUT engages upon subsequent encounters CD cluster of differentiation defines specific ersts secondary/ tertiary responses example: CD4 helper T-cell CD8= aytotoxic T-cell B-cell/B-Lymphocyte: defining characteristic presense of B-cell receptor on cell surface B-cell receptor membrane bound antibody ~200.000 receptors on each B-cell cach B-cell has its own specificity each sell recognizes its own particular antigen and NOTHING else antigen binds to receptor B-cell scoretes antibody B-cell becomes known as plasma cil T-cell / T-Lymphocyte: CD4+ Helper T-cells CD8+ Cytotoxic T-cells Defining characteristic: presence of T-cell receptor Natural Killer (NK) / Innate Lymphoid Cell (ILC) Originate from lymphoid origin Active part of the innate immune system Look for cells that do not belong / potentially dangerous / senescent (old cells) Important in tumor defense and recycling senescent cells Employs Antibody-Dependent Cell Cytotoxicity (ADCC) Primary Lymphoid Organs Primary Lymphoid Tissue: The site of development and maturation of lymphoid cells (and all immune cells really) Types: Bone Marrow Thymus Bone Marrow Parenchyma: The functional tissue of an organ as distinguished from the connecting and supporting tissue Stroma: Everything that is not parenchyma Microenvironment / niche in bone parenchyma Stromal Cells: Endothelial cells Perivascular cells Sympathetic nerves Macrophages Osteoblasts ALL IMMUNE CELL DEVELOPMENT BEGINS IN THE BONE MARROW! Site for long lasting memory B and T cells