Haematology Lec 5 New PDF

HEMATOLOGY Dr. Rayan Khalid  Immunology Immunology: Study of the components and function of the immune system  Immune System A network collected from cells, tissues organs and soluble factors that work together and provide non- specific a...

HEMATOLOGY Dr. Rayan Khalid  Immunology Immunology: Study of the components and function of the immune system  Immune System A network collected from cells, tissues organs and soluble factors that work together and provide non- specific and specific protection to defend body against attacks of: Foreign pathogenic microbes Microbial toxins Tumor cells Crucial to human survival  The Structure of Immune System Organs of the immune system are positioned throughout the body. Molecules, cells and tissues that mediate responses to foreign substances All parts of the body that help in the recognition and destruction of foreign material e.g:  Recticulo-endothelial system (RES) : Allows immune cells to bind and move outside the blood & lymphatic system. Extracellular fluids system (ECF): Enables immune cells to move. Blood, vascular (circulatory) system. Lymphatic system. Lymphoid organ Lymphoid organs are home to lymphocytes (the key players). Primary (central ) lymphoid organs - Bone marrow and thymus where lymphocytes are generated (maturation site) Secondary (peripheral ) lymphoid organs -where adaptive immune responses are initiated ( spleen , lymph nodes, lymphocyte proliferation, etc. )  Functions of Immune System Defending against invading pathogens Remove damaged tissues Identifying and destroying abnormal or mutant cells (immune surveillance - the primary defense mechanism against cancer).  Immunity It is the ability of body to resist different types of pathogenic agents like bacteria, virus, toxic substances, etc. State of non-specific and specific protection Immunity is of two types: Innate immunity. Acquired immunity. Innate immune system  Innate (non-specific) immunity o The capacity of the body to resist pathogens entry and eliminates them before the development of any disease. o The first line of defense against any type of pathogens. o Include: epithelial barriers, phagocytes, plasma and complement proteins Responses Immediate combat microbes Instruct adaptive immune system Dead tissue clearance Initiate repair General features ⚫ Distinguishes cells and molecules that belong within the body (self) from those that do not (non-self) ⚫ Defensive functions with a restricted set of reactions ⚫ Does not generate immunogenic memory Components of innate immune system Complements ⚫ Collection of proteins that are important in defense against microbes. ⚫ Humoral arm of innate immune system. ⚫ Many complement proteins are proteolytic enzymes. ⚫ The complement cascade may be activated by any of three Pathways. ⚫ Complement system serves three main functions in host defense: ⚫ Opsonization: coating a microbe d by C3b lead to rapidly ingested ⚫ Inflammation: fragments of complement proteins, {C5a and C3a} , are chemo-attractants for leukocytes, they promote leukocyte recruitment ⚫ Cell lysis: by formation of a protein complex that inserts into the microbial cell membrane, osmotic lysis (C5b, C6- C9) Adaptive immune system  Adaptive (specific) immunity o resistance developed in the body against any specific foreign body like bacteria, viruses, toxins, vaccines or transplanted tissues. o It is the most powerful immune mechanism o Lymphocytes are responsible for adaptive immunity o Types : o Cellular immunity: activation of cells o Humoral immunity: mediated by macro molecules found in ECF Innate vs adaptive immune system  Development and processing of lymphocytes lymphocytes develop from the bone marrow differentiated into two categories. T lymphocytes (T cells): responsible for cellular immunity B lymphocytes (B cells) responsible for humoral immunity. B LYMPHOCYTES Constituent 20% of lymphocyte. Types of B Lymphocytes: Plasma cells. Memory cells. Storage: in the lymphoid tissues of lymph nodes, spleen, bone marrow and the GI tract. T LYMPHOCYTES Constitute about 80% of blood lymphocytes. T lymphocytes are processed in thymus. Types of T Lymphocytes: T- Helper cells or inducer T cells(CD4 cells) T- Cytotoxic cells or killer T cells (CD8 cells) Suppressor T cells. Memory T cells. Cell-mediated Immunity Types of T cells  CD8+ T cells: (cytotoxic T lymphocyte, CTL): they are directly cytotoxic.  CD4+ T cells (T helper cells (Th cells): help B lymphocytes and cytotoxic T cell to differentiate and proliferate. Functions of Cellular immunity Cellular immunity is actively involved in: Rejection of tissues or organ graft. Delayed hyper sensitivity reaction. Anti-tumour immunity. Cooperation with B cell in humoral immunity. Adaptive Humoral immunity B Cells and Humoral immunity  B Cells Constituent 20% of lymphocyte.  The humoral response is carried out by antibodies which are produced by Plasma cells.  Plasma cells are derived from activated B-cells that are produced in the bone marrow  Memory cells The secondary response that is carried out by memory cells is different in : Memory cells produce antibodies that bind with greater affinity to their antigens than the antibodies produced in the initial response. The response time is much vaster than the primary response A greater number of antibodies are produced.  Antibodies  Are proteins that are formed and secreted by Activated B cells or mature B cells, (Plasma Cells).  They are known as Immunoglobulins  They come in various classes e.g. AMGED. Function of Antibodies  Opsonization: Coating antigen with antibody enhances phagocytosis  Neutralization: blocks adhesion of bacteria and viruses to mucosa. Also blocks active site of toxin  Activation of complement  Increases inflammation through the byproducts of the complement system (C5a and C3a) Structure of an Antibody  Antibody composed of two heavy chains and two light chains bind together to make a Y shaped molecule  The two sections located at the ends of Y’s arms are called variable (V) regions.  The stem of the antibody molecule as well as the lower portion of the arms called constant (c) regions {5 major types ). IgD  Found on surface of mature B-cells.  Biological function unknown (thought to function in activation of B-cells) IgM IgM expressed as membrane bound antibodies on B-cells Pentamer (5 units) First immunoglobulin class produced in a primary response to an antigen effective at stimulating complement and opsinization Large-size - does not diffuse well IgG ▪ Most abundant isotype in serum (80%) ▪ Cross placenta and play important role in protecting fetus ▪ Provides passive immunity to unborn fetus. ▪ Activate complement system ▪ Opsonin—phagocytosis IgE Mediate the immediate hypersensitivity reactions (hay fever, asthma, hives, anaphylactic shock) Mast cells and basophils bind fc portion of IgE IgA  Most abundant Ab in the body  Found Predominantly in external secretions i.e. Breast Milk, Saliva, tears, mucus.  Plasma cells that release IgA Abs are concentrated along the Mucus Membrane surface.  Provides passive immunity to infants through mothers breast milk