Anne and Tresha
Thursday,
December 2, 2004
Central = Primary lymphoid tissue
• Site of maturation of the cells of the immune system• Thymus
– encapsulated– T cells
• Bone marrow– Bursal equivalent– B cells, monocytes, erythrocytes, granulocytes, and megakaryocytes
Peripheral = Secondary lymphoid tissue
• Filter blood and lymph• Site of antigen, immune system interaction
Peripheral = Secondary lymphoid tissue
• Diffuse lymphatic tissue (Unencapsulated)– Found in the lamina propria where pathogens
are likely to invade– GI: Tonsils, Peyer’s patches, appendix;
Respiratory tract; GU
• Lymph nodes– Encapsulated– Interposed btwn lymphatic vessels (only)
• Spleen lymphatic tissue– Encapsulated– Interposed btwn lymph and blood circulation
Lymph Vessels
• Valves• Carries Lymph from tissue
lymph nodes blood via thoracic duct– Fluid– Proteins– Ingested fats– Particulate matter– Antigen– Disease microorganisms– Cells (normal and cancerous)
Lab 11 Slide 7
Primary follicle- Naïve Lymphocytes- No germinal center
Secondary follicle- Germinal Center- Antigen has been
encountered- Looks pale! - because
of plasmablasts Lab 11 Slide 9
1
2
• Germinal Center– Dark zone = densely
packed lymphocytes separated by reticular cells
– Light zone = plasmablasts
– T cells at periphery
Tonsil
• Unencapsulated
• Stratified squamous non-keratinized epithelium
• Dense fibrous CT• CT Septum --> lobes• Crypts - invaded by
lymphocytes• Numerous Lymphoid
nodules– Germinal centers
• Lymphocytes invade the epithelium and the connective tissue
• GALT (gut associated lymphatic tissue)– In the loose areolar CT of the lamina propria– Diffuse lymphatic tissue– Solitary lymphatic nodules– Aggregates of lymphatic nodules (Peyer’s patches
and appendix)
A
B
Question 1C.Both
D.Neither
A
B
Question 1C.Both
D.Neither
Tonsil
Lymph node
• Is encapsulated = B• Contains germinal centers = C• Peripheral lymphoid tissue = C• Central lymphoid tissue = D
Question 2The region at the arrow is:
A) Peyer’s Patch
B) Germinal Center
C) Lymph Node
D) Primary lymphoid nodule
Question 2The region at the arrow is:
A) Peyer’s Patch
B) Germinal Center
C) Lymph Node
D) Primary lymphoid nodule
Lymph Node Function
• Filters lymphatic fluid• Enhance antigen presentation• Facilitate B-Cell Activation to
generate plasma cells and memory B-cells
Lymph Flow w/in Node
Afferent Lymphatics Subcapsular sinus trabecular sinuses medullary sinus efferent lymphatics
Lymph Node Structural Components
• Capsule: Dense, Irregular CT
• Trabeculae are extensions of the capsule
• Reticular cells- framework (stain black with the Silver stain)
• Hilum- efferent lymphs; entry
and exit of blood vessels
Lymph Node Parenchyma
• Cortex
– Primary, secondary nodules
• Deep cortex
• (aka paracortex, juxtamedullary cortex, thymus dependent cortex)
– No nodules
• Medulla
– Cords and sinuses.
– Where plasma cells synthesize and release Abs into lymph flowing through the sinuses.
Lymphatic Sinuses• Subcapsular sinus
– Receive lymph from afferent lymphatic vessels
• Trabecular sinuses– Drain into medullary sinuses
• Provide open communication between lymphatic drainage and parenchyma (macrophages monitor lymph as it percolates through; will phagocytose)
• Macrophages take up India ink- stained black.
The Germinal Center
• Characterizes the 2ndary nodule
• Pale staining center: plasmablasts
– Large cells, large nucleus, prominent nucleolus
– May see mitotic figures
• Dark outer zone
– Densely packed lymphocytes (sp. B-cells)
T-Cell Zone
• Comprises Deep Cortex and Paracortex
• Where T and B cells enter from the circulation
• See post capillary venules with high endothelial cells
• B cells migrate, T cells remain
Medullary Region
• Cords and Sinuses• Cords: reticular cells,
lymphocytes, plasmablasts, plasma cells
• Antibody secreted into efferent lymph
• Macrophages present• Entry/Exit of blood
vessels, nerves, efferent lymph
Summary of Lymph Node flow
Lymph Flow w/in Node
Afferent Lymphatics Subcapsular sinus trabecular sinuses medullary sinus efferent lymphatics
Question 3
The region inside the box contains which of the following upon antigenic stimulation:
A. Plasma Cells
A. Macrophages
B. T-Cells
C. Memory B-Cells
D. All of the Above