Download Defence Systems 2

Immune-Lymphatic System – 2
Lymphatic Organs
ANHB 2212 – 2008
Avinash Bharadwaj
Recognition of Antigens
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The Antigen Presenting Cell (APC)
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Macrophage
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Phagocytosis
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Fragmentation of foreign material
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Attachment to cell surface molecules (MHC)
Other APCs
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Many sites, many types
Example : Langerhans cells in the epidermis.
Lymphocytes
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Two major types – T and B lymphocytes
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Not distinguished by LM
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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
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“Cell mediated” immunity.
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Cytotoxic T cells – Perforin, Lympotoxin, TNF
Helper T cells
Suppressor T cells
Memory
Humoral immunity
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B lymphocytes  plasma cells (abundant rER)
Memory B cells
Helper T cells
Exposure and Barriers
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External surface – skin
The “open” systems
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The epithelial barrier
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Digestive and Respiratory systems – most exposed
Urogenital (to a lesser extent)
Integrity of epithelium
Intra-epithelial defence cells
Antibodies
“Local” infections and non-specific defence
Beyond the barrier…
Blood, Tissue Fluid and Lymph
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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
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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), tonsillar
tissue.
Organised, encapsulated structures
 Lymph nodes
 Spleen – special functions
 Thymus – the academy
Lymphatic Nodule
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“Non-capsulated”
Single or aggregated
Independent
OR
parts of other lymphoid
organs
Outer dark zone
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(Corona or cap)
Germinal centre
Lymphocyte Training – Thymus
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Lymphoid organ
Anterior Mediastinum
Foetal life  Childhood  Puberty
Involution in adult life
Thymus
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Hassal’s
Corpuscles
Capsule
Lobules
Cortex
Medulla
Regions and Cells
Capsule
Cortex
Epithelial
reticular cells
Lymphocytes
Stages of
maturation
Medulla
Blood vessels
Barrier
Lymphocyte
Training
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CFU-L
Recognise antigen –
pass/fail
Recognise self/non-self
– pass/fail
Cytotoxic / Helper T
cells
B Lymphocytes
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Bursa of Fabricius
 Lymphoid organ in birds
Bursa equivalent structures
Bone marrow
 Gut and other mucosa-associated
structures
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Tonsil
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A group of lymphoid
structures
Around the pharynx
(GIT and RS)
Lingual, “palatine”,
tubal,
nasopharyngeal
Structurally similar
Palatine Tonsil
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Epithelium of the
pharynx
“Crypts”
Lymphatic nodules
Connective tissue and
pharyngeal muscle.
Peyer’s Patches
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Ileum – “antimesenteric border”
Lamina propria  submucosa
Lymph Node
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Capsulated
Afferent lymphatics  “subcapsular sinus”
Hilum – blood vessels, efferent lymphatic
Cortex and medulla
Cortex
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Lymphatic nodules, germinal centres
“Paracortex”
Medulla
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Medullary cords and sinusoids
C
M
Lymph Node
Lymphatics
 Afferent
 Efferent
Blood vessels
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A
A
A
E
Lymphocytes
Cortex
A
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Nodules (B)
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Deep cortex (T zone)
sinuses)
Medulla (Cords,
Function
Antigens etc
APCs
Nodule : B
High Endothelial Vv
Medulla : Plasma
cells etc
Spleen
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Lymphatic function
– lymph nodules
(white pulp)
around arterioles.
Red pulp
Sinusoids
Last Slide