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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 - PowerPoint PPT Presentation
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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
Emphasis : histological structure of lymphoid organs
Lecture 1 : 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
Lymphocytes, macrophages, plasma cells, other leucocytes Outer zone (corona) and germinal centre
Aggregates of lymphatic nodules 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
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More next week!