Immunology Cellular basis of imunity 1 of 2 week 13.pptx

INTRODUCTION TO THE IMMUNE SYSTEM LECTURES 1 & 2 : Cells and tissues of the Immune System LECTURES 3 & 4 & 5: Introduction to Innate & Adaptive Immunity LECTURE 6: Introduction to Disorders of Immunity Introduction Immunology is the study of immunity (the response of the immune system to infecti...

INTRODUCTION TO THE IMMUNE SYSTEM LECTURES 1 & 2 : Cells and tissues of the Immune System LECTURES 3 & 4 & 5: Introduction to Innate & Adaptive Immunity LECTURE 6: Introduction to Disorders of Immunity Introduction Immunology is the study of immunity (the response of the immune system to infection). There are two arms to the immune response: 1. Innate response 2. Adaptive response first line of final stage of defense immune response non-specific specific no memory memory Introduction Effector mechanisms utilised by innate and adaptive responses are the same. The adaptive response evolved from the innate response. Inflammation is present throughout an immune response (both innate and adaptive) and is a result of the response. Introduction Effector mechanisms: Mechanisms by which harmful agents are destroyed by the immune system. Can be both: 1. Cell-mediated - effector function is performed by a cell e.g. cytotoxic T cell (Tc), phagocyte, natural killer (NK) cell. 2. Humoral - effector function is mediated by soluble molecules e.g. complement, cytokines, acute phase proteins, antibodies. Cells of the Immune System  Mononuclear phagocytes (monocytes / macrophages), dendritic cells, polymorphonuclear granulocytes (neutrophils, eosinphils, basophils), mast cells, lymphocytes (B and T cells and natural killer cells). All develop from a common precursor stem cell in the bone marrow (BM) with the exception of T cells which complete their maturation in the thymus. Cells of the Immune System 1. Mononuclear phagocytes (monocytes / macrophages): (mononuclear leucocytes) Originate in BM and enter the peripheral blood as monocytes. Monocytes leave the circulation and enter tissues where they mature into macrophages (histiocytes). Cells of the Immune System Monocytes are the blood precursors of tissue macrophages. 0.2 – 0.8 x 109/l 12 – 17 mm diameter, oval – kidney bean shaped nucleus. Monocyte life span in blood = few days Macrophages can live for years in tissues. Cells of the Immune System Macrophages are activated by a variety of stimuli and may assume different forms e.g. giant cells. Macrophages are found in all organs and tissues and in certain locations have specific names: e.g. in the CNS - microglia in the liver - Kupffer cells in the lungs - alveolar macrophages in the kidney - mesangial cell. Cells of the Immune System Functions in immunity: a) phagocytosis of foreign particles (undergo multiple rounds) b) production of inflammatory mediators c) APC - presentation of antigen to T cells which initiates an adaptive response. Mediate both innate and adaptive responses. Reticuloendothelial cells is the old name for mononuclear phagocytes and their tissue distribution the reticuloendothelial system (RES). monocyte Tissue macrophage Macrophage ingesting bacterium Cells of the Immune System Dendritic cells: Accessory cells that induce the adaptive response. Two main cell types: a) Interdigitating dendritic cells - present in most organs and epidermis of skin where they are called Langerhans cells. Thought to arise from marrow precursors related to mononuclear phagocytic system. Cells ofinthe Immune System Function Immunity: Pick up antigens and transport them to lymph nodes to initiate an adaptive response. Present antigen to T cells. Mediate adaptive responses. b) Follicular dendritic cells - restricted to lymphatic tissue. Do not originate in BM. Unrelated to interdigitating dendritic cells. Function in Immunity: Present antigen to B cells. Mediate adaptive responses Dendritic cells Cells of the Immune System Granulocytes: Contain abundant cytoplasmic granules. Include neutrophils, eosinphils and basophils. 1. Neutrophils (polymorphonuclear leukocytes): Multi-lobed (3 – 5 lobes usually) morphologically diverse nuclei. Most abundant granulocyte (2.5 – 7.5 x 109/l) Cells of the Immune System 12 – 15 mm diameter Life span 10 h (blood), days in tissues. Functions in Immune response Highly phagocytic. Key cells in anti-bacterial responses Mediate innate response and support adaptive responses. Peripheral Blood Films showing PMN leucocyte (neutrophil) Cells of the Immune System 2. Eosinophils: Bi-lobed nucleus and acidophilic granules. 0.04 – 0.4 x 109/l. Life span = 2 weeks. Acidic - staining granules that bind eosin and stain orange Granules contain major basic protein. Bilobed nucleus Cells of the Immune System Functions in immunity: Function primarily in the elimination of infectious agents such as helminth worms. Also mediate hypersensitivity (allergic) reactions – mediate adaptive responses. eosinophil Cells of the Immune System 3. Basophils: Basophilic granules. Mediate hypersensitivity reactions through release of chemicals such as histamine. 0.01 – 0.1 x 109/l Only occasionally seen in normal peripheral blood. Nucleus obscured by basophilic specific granules. Cells of the Immune System Dark basic staining granules containing heparin and histamine – stain purple) Role in Immunity Support mast cells in tissues and mediate allergic reactions – mediate adaptive responses