Transcript Document
Immune-Lymphatic System - 1 Introduction and Organisation 212 – 2004 – Week 8 Avinash Bharadwaj Immunology Et cetera… Defence mechanisms of the body Perspectives Molecular Cellular Histological Gross anatomical Immunology Et cetera… A vast and complex field Introduction and overview Lecture 1 : Emphasis : histological structure of lymphoid organs Simple concepts Lymphatic nodules, Tonsil, Lymph node Lecture 2 : Spleen and Thymus Further elaboration of immune processes “Getting Rid Of ”… External attackers Viruses, bacteria, parasites… Other “foreign” substances Particulate matter and chemicals Our own dead cells Wayward cells An unfortunate sidelight – our own normal cells Mechanisms Nonspecific defence Specific defence Cellular attack Molecular (“humoral”) attack More than one mechanisms may be operating at a time! Cells involved White blood cells Macrophages Lymphocytes Others Intricate interactions between cells – molecular messengers WBCs – Quick Review Granulocytes Cytoplasmic granules Neutrophilic, eosinophilic or basophilic Agranulocytes Lymphocytes Monocytes Nonspecific Defence Neutrophils Movement out of capillaries Phagocytosis and “digestion” Expendable force Action localised to site of infection Other granulocytes… Specific Defence - Immunity Recognition of “non-self” or “foreign”. Attack Memory Terminology Antigen – a foreign substance Often (but not always) protein. Antibody – a protein (γ-globulin) that specifically combines with an antigen. Recognition of Antigens The Antigen Presenting Cell Macrophage Phagocytosis Fragmentation of foreign material Attachment to cell surface molecules (MHC) MHC (Major Histocompatibility Complex) Proteins unique to each individual (Originally recognised in the context of tissue transplantation) MHC Class I molecules present in all nucleated cells MHC Class II – in APCs – Serve to bind antigens Lymphocytes Two major types – T and B lymphocytes Not distinguished by LM Two types of immune responses Cell mediated – direct attack by cells Humoral – antibodies as the medium (Humor : fluid. Antibodies are transported by the blood and also present in certain secretions)) T Lymphocytes “Cell mediated” immunity. Helper T cells Interleukins : relevant responses from other cells Cytotoxic T cells – Perforin, Lympotoxin, TNF Suppressor T cells – Interleukins control the reaction Memory B Lymphocytes Humoral immunity Helper T cells Interleukins activation – mitosis large number of B cells against the same antigen. B lymphocytes plasma cells (abundant rER) Antibodies work in various modes Memory B cells Exposure and Barriers External surface – skin The “open” systems Digestive and Respiratory systems – most exposed Urogenital (to a lesser extent) The epithelial barrier Integrity of epithelium Chemical factors Intra-epithelial defence cells Antibodies “Local” infections and non-specific defence Beyond the barrier… Blood, Tissue Fluid and Lymph Blood capillaries “Extravasation” of fluid Tissue fluid and exchange Not all the fluid returns to blood vessels. Lymph flows through lymphatic vessels before returning to larger veins. Lymphoid (Lymphatic) Tissues Scattered lymphocytes and other cells Lymphatic nodule – structural organisation Aggregates of lymphatic nodules Lymphocytes, macrophages, plasma cells, other leucocytes Outer zone (corona) and germinal centre Mucosa of GI Tract, respiratory system and other sites Larger aggregates – Peyer’s patches (ileum), tonsilar tissue. Organised, encapsulated structures Lymph nodes Spleen – special functions Thymus – the academy Lymphatic Nodule Outer dark zone (Corona or cap) Germinal centre Tonsil A group of lymphoid structures Around the pharynx (GIT and RS) Lingual, “palatine”, tubal, nasopharyngeal Structurally similar Palatine Tonsil Epithelium of the pharynx “Crypts” Lymphatic nodules Connective tissue and pharyngeal muscle. Peyer’s Patches Ileum – “antimesenteric border” Lamina propria submucosa Lymph Node Capsulated Afferent lymphatics “subcapsular sinus” Hilum – blood vessels, efferent lymphatic Cortex and medulla Cortex Lymphatic nodules, germinal centres “Paracortex” Medulla Medullary cords and sinusoids C M More next week!