ImmuneLymphatic System 1 Introduction and Organisation

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Immune-Lymphatic System - 1 Introduction and
Organisation

• 212 2005 Week 8
• Avinash Bharadwaj

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Immunology A vast and complex field

• Defence mechanisms of the body
• Perspectives
• Molecular
• Cellular
• Histological
• Gross anatomical
• 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

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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

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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

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WBCs Quick Review

• Granulocytes
• Cytoplasmic granules ?
• Neutrophilic, eosinophilic or basophilic

• Agranulocytes
• Lymphocytes
• Monocytes

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Nonspecific Defence

• Neutrophils
• Movement out of capillaries
• Phagocytosis and digestion
• Expendable force
• Action localised to site of infection

• Other granulocytes

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Specific Defence - Immunity

• Recognition of non-self or foreign.
• Attack
• Memory

• Terminology
• Antigen a foreign substanceOften (but not
  always) protein.
• Antibody a protein (?-globulin) that
  specifically combines with an antigen.

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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

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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))

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Cellular and Humoral Immunity

• Cell mediated immunity.
• Cytotoxic T cells Perforin, Lympotoxin, TNF
• Helper T cells
• Suppressor T cells
• Memory
• Humoral immunity
• B lymphocytes ? plasma cells (abundant rER)
• Memory B cells
• Helper T cells

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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
• Intra-epithelial defence cells
• Antibodies
• Local infections and non-specific defence
• Beyond the barrier

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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.

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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 Peyers patches (ileum),
  tonsillar tissue.
• Organised, encapsulated structures
• Lymph nodes
• Spleen special functions
• Thymus the academy

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Lymphatic Nodule

• Non-capsulated
• Single or aggregated
• Independent OR parts of other lymphoid organs
• Outer dark zone
• (Corona or cap)
• Germinal centre

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Tonsils

• A group of lymphoid structures
• Around the pharynx (GIT and RS)
• Lingual, palatine, tubal, nasopharyngeal
• Structurally similar
• Epithelium of the pharynx
• Crypts
• Lymphatic nodules
• Connective tissue and pharyngeal muscle.

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Peyers Patches

• Ileum antimesenteric border
• Lamina propria ? submucosa
• Best seen in younger subjects

Smaller aggregates present under many mucous
membranes Mucosa Associated Lymphoid Tissue
or MALT
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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

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C
M
More next week!