Tissue and Cells of the Immune System PDF

L19 HPS-305 Tissue and cells of the immune system Presented by Dr Sarah Abusham Learning objectives Define the immune system know the tissue of the immune system Identify and list the cells of the immune system Know the function of the immune cells Know the types and fu...

L19 HPS-305 Tissue and cells of the immune system Presented by Dr Sarah Abusham Learning objectives Define the immune system know the tissue of the immune system Identify and list the cells of the immune system Know the function of the immune cells Know the types and function of the B & T lymphocyte. www.vision.edu.sa The immune system The immune system is a highly specialized and complex network of tissues, cells, and molecules that work together to defend the body against infections, foreign substances, and abnormal cells, such as cancer cells www.vision.edu.sa Presentation Title | Chapitre Title Innate immunity Adaptive immunity ( Humeral & Cell-mediated) Components Components Macrophages antigen presenting cells Granulocytes T-cells Natural killer cells B-cells Complement Antibodies Other chemicals: HCL, lysozyme Complement Characteristics Characteristics * Action is immediate *Action requires days to develop * Response is non-specific *Response is specific * Response is not enhanced on * Response is enhanced on repeated exposure to pathogen repeated exposure to pathogen www.vision.edu.sa  Immune System Tissues Primary Lymphoid Organs These are the sites where immune cells develop and mature. Bone Marrow: The site of haematopoiesis (production of all blood cells, including immune cells). Produces B cells (which mature here) and immature T cells. Thymus: Site where T cells mature and undergo selection to become functional. www.vision.edu.sa  Secondary Lymphoid Organs These are the sites where immune responses are initiated. Lymph Nodes: Filter lymphatic fluid and house immune cells to detect and respond to antigens. Spleen: Filters blood, removing pathogens, old red blood cells, and debris. Contains white pulp (immune function) and red pulp (recycling red blood cells). Mucosa-Associated Lymphoid Tissue (MALT): Includes tissues like the tonsils, Peyer’s patches (in the intestine), and appendix. Provides localized immune defense at mucosal surfaces. Skin-Associated Lymphoid Tissue (SALT): Immune components in the skin provide protection against pathogens that breach the skin barrier. www.vision.edu.sa  Cells of the Immune System innate Immune Cells (Immediate, non-specific response) Neutrophils: Rapid responders that engulf and destroy bacteria and fungi. Macrophages: Large phagocytes that engulf pathogens and dead cells, and present antigens to T cells. Dendritic Cells: Professional antigen-presenting cells that link the innate and adaptive immune systems. Natural Killer (NK) Cells: Destroy virus-infected and abnormal cells by inducing apoptosis. Mast Cells: Release histamine and other chemicals during allergic responses and inflammation. Eosinophils: Involved in combating parasitic infections and allergic reactions. Basophils: Release inflammatory mediators and play a role in allergies. www.vision.edu.sa Adaptive Immune Cells (Specific, slower response, but with memory) B Lymphocytes (B cells): Produce antibodies that neutralize pathogens. Differentiate into plasma cells (antibody-producing cells) and memory B cells. T Lymphocytes (T cells): Helper T cells (CD4+): Activate other immune cells, including B cells and cytotoxic T cells. Cytotoxic T cells (CD8+): Kill virus-infected and cancerous cells. Regulatory T cells: Suppress immune responses to maintain tolerance and prevent autoimmunity. Memory T cells: Long-lived cells that provide faster responses upon re-exposure to antigens. www.vision.edu.sa Other Immune Cells Monocytes: Precursors to macrophages and dendritic cells; circulate in the blood. Platelets: Involved in blood clotting and release immune mediators during inflammation. www.vision.edu.sa  Antigen-presenting cells (APCs) Are specialized immune cells that process and present antigens to T cells, initiating an adaptive immune response. Examples :- Dendritic Cells (DCs): The most effective APCs for activating T cells. Found in tissues that interact with the external environment (e.g., skin, Macrophages: mucosa). Migrates to lymph nodes after capturing antigens. B Cells: www.vision.edu.sa  Cells of the imm une syste m Lymphocytes Mediators of adaptive immune responses; only cells with specific receptors for antigens. Antigen-presenting cells (APCs) Specialized to capture, concentrate, and display antigens for recognition by lymphocytes Dendritic cells; macrophages, B cells. Effector cells Function to eliminate microbes; include lymphocytes, granulocytes (neutrophils, eosinophils), macrophages www.vision.edu.sa Lymphocytes the primary cells of the lymphoid s ystem Types of lymphocytes T cells (thymus-dependent) B cells (bone marrow-derived) NK cells (natural killer) www.vision.edu.sa T lymphocyte 80% of circulating lymphocytes Some of the types: Cytotoxic T cells (CD8): attack foreign cells or body cells infected by viruses (“cell-mediated immunity”) Regulatory T cells (CD4): Helper T cells and suppressor T cells (control activation and activity of B cells) www.vision.edu.sa The CD Nomenclature cluster of differentiation (CD) The CD (Cluster of Differentiation) nomenclature is a standardized system used to classify and identify molecules on the surface of immune cells, including lymphocytes CD molecules (CD antigens, CD markers) are: Used to classify leukocytes into functionally distinct subpopulations, e.g. helper T cells are CD4+CD8-, CTLs are CD8+CD4- Often involved in leukocyte functions www.vision.edu.sa T-lmphocytes migrate from bonE marrow to enter thymus 1) In the outer cortex of thymus: - T-lymphocytes acquire specific receptors (TCRs) - This receptor commit lymphocyte to a single antigen. -T lymphocytes become CD4+ (helper T cells) or * CD8+ cells (which in turn can become killer T cells) also called cytotoxic T cells www.vision.edu.sa 1) CD4 T helper lymphocytes Subsets Th1 produce mainly : - Cytokines of CMI and inflammation e.g. IFN-γ, TNF- β, IL-3 and IL-2 TH2 produce mainly: - Cytokines that stimulate B-cells - Suppressor cytokines e.g. Il-4, IL-5, IL-6 and IL-10 www.vision.edu.sa 2) CD8 Cytotoxic T-lymphocytes (CTLs) * They constitute 35% of peripheral T-cells * CTLs recognize antigen on suurface of target cells (infected APC ) in association with MHC-I * They are activated and kill the virus infected cell or tumour cell www.vision.edu.sa  The Life Of The B Cell B lymphocytes are formed within the bone marrow and undergo their development there They have the following functions: To interact with antigenic epitopes, using their immunoglobulin receptors To subsequently develop into plasma cells, secreting large amounts of specific antibody, or To circulate as memory cells To present antigenic peptides to T cells. www.vision.edu.sa * Immature B cells express IgM receptors on the surface * Mature B cells express IgM, IgD molecules on surfaces * IgM and IgD molecules serve as receptors for antigens * B-cells bear receptors for Fc portion of IgG and a receptor for C3 component of the complement www.vision.edu.sa  B Lymphocytes The receptor for antigens is an antibody on B cell surface. B cell identifies pathogens when antibodies on its surface bind to a specific foreign antigen. This antigen/antibody complex is taken up by the B cell and processed by proteolysis into peptides (small pieces). As the activated B cell then begins to divide (“clonal expansion”), its offspring secrete millions of copies of the antibody that recognizes this antigen These antibodies circulate in blood plasma and lymph, bind to pathogens expressing the antigen and mark them for destruction by complement activation or for uptake and destruction by phagocytes. www.vision.edu.sa www.vision.edu.sa Antibody www.vision.edu.sa Natural Killer (NK) Cells 5-10% of circulating lymphocytes Attack foreign cells, normal cels infected with viruses, cancer cells that appear in normal tissues Known as “immunologic surveillance”. www.vision.edu.sa Thank You www.vision.edu.sa