1. Immune-Lymphatic System – 2 Lymphatic Organs
ANHB 2212 – 2008
Avinash Bharadwaj

2. Recognition of Antigens
The Antigen Presenting Cell (APC)
Macrophage
Phagocytosis
Fragmentation of foreign material
Attachment to cell surface molecules (MHC)
Other APCs
Many sites, many types
Example : Langerhans cells in the epidermis.

3. 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)

4. 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

5. 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…

6. 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.

7. 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), tonsillar tissue.
Organised, encapsulated structures
Lymph nodes
Spleen – special functions
Thymus – the academy

8. Lymphatic Nodule “Non-capsulated” Single or aggregated
Independent OR parts of other lymphoid organs
Outer dark zone
(Corona or cap)
Germinal centre

9. Lymphocyte Training – Thymus
Lymphoid organ
Anterior Mediastinum
Foetal life  Childhood  Puberty
Involution in adult life

10. Thymus
Capsule
Lobules
Cortex
Medulla
Hassal’s Corpuscles

11. Regions and Cells Epithelial reticular cells Capsule Cortex
Lymphocytes
Stages of maturation
Blood vessels
Barrier
Capsule
Cortex
Medulla

12. Lymphocyte Training CFU-L Recognise antigen – pass/fail
Recognise self/non-self – pass/fail
Cytotoxic / Helper T cells

13. B Lymphocytes Bursa equivalent structures Bursa of Fabricius
Lymphoid organ in birds
Bursa equivalent structures
Bone marrow
Gut and other mucosa-associated structures

14. Tonsil A group of lymphoid structures Around the pharynx (GIT and RS)
Lingual, “palatine”, tubal, nasopharyngeal
Structurally similar

15. Palatine Tonsil Epithelium of the pharynx “Crypts” Lymphatic nodules
Connective tissue and pharyngeal muscle.

16. Peyer’s Patches Ileum – “antimesenteric border”
Lamina propria  submucosa

17. 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

18. C M

19. Lymph Node Blood vessels Cortex Lymphatics Afferent Efferent A A
Lymphocytes
Cortex
Nodules (B)
Deep cortex (T zone) Medulla (Cords, sinuses) A A A E A

20. Function Antigens etc APCs Nodule : B High Endothelial Vv
Medulla : Plasma cells etc

21. Spleen
Lymphatic function – lymph nodules (white pulp) around arterioles.
Red pulp
Sinusoids

22. Last Slide