1. Yixing Xu Wednesday, November 30, 2005

2. Central = Primary lymphoid tissue Site of maturation of the cells of the immune system Bone marrow –B cells, monocytes, erythrocytes, granulocytes, and megakaryocytes Thymus –T cells Peripheral = Secondary lymphoid tissue Filter blood and lymph Site of antigen, immune system interaction

3. Peripheral = Secondary lymphoid tissue Diffuse lymphatic tissue –Unencapsulated –GI (Tonsils*, Peyer’s patches*, appendix); Respiratory tract; Genitourinary –Found in the lamina propria where pathogens are likely to invade Lymph nodes –Encapsulated –Interposed btwn lymphatic vessels (only) Spleen lymphatic tissue –Encapsulated –Interposed btwn lymph and blood circulation

4. Follicle = Nodule Primary follicle -Naïve (B) Lymphocytes -No germinal center Secondary follicle -Germinal Center -Antigen has been encountered -Looks pale because of plasmablasts: large euchromatic nuclei -Surrounded by T cells 2 1

5. Germinal Center –Dark zone = densely packed B lymphocytes separated by reticular cells –Light zone = plasmablasts Large cell, central nucleus, prominent nucleolus –T cells at periphery

6. Tonsil Unencapsulated Stratified squamous non- keratinized epithelium In the dense fibrous CT CT Septum  lobes Crypts - invaded by lymphocytes Numerous Lymphoid nodules –Primary: homogeneous –Secondary: germinal centers

7. Lymphocytes invade the epithelium and the connective tissue

8. GALT (gut associated lymphatic tissue) –Unencapuslated: diffuse lymphatic tissue –In the loose areolar CT of the lamina propria –Solitary lymphatic nodules Aggregates of lymphatic nodules in Peyer’s patches and appendix

9. Question 1 The region at the arrow is: A) Peyer’s Patch B) Germinal Center C) Lymph Node D) Primary lymphoid nodule

10. Question 1 The region at the arrow is: A) Peyer’s Patch B) Germinal Center C) Lymph Node D) Primary lymphoid nodule

11. Lymph Node Function Filters lymphatic fluid Enhance antigen presentation Facilitate B-Cell Activation to generate plasma cells and memory B-cells

12. Lymph Node Structural Components Capsule: Dense, Irregular CT (collagen type I stains red brown) Trabeculae are extensions of the capsule Reticular tissue - framework (collagen III stains black with the Silver stain) Hilum - efferent lymph; entry and exit of blood vessels

13. Lymph Flow w/in Node Afferent Lymphatics  subcapsular sinus  trabecular sinuses  medullary sinus  efferent lymphatics

14. Lymph Vessels Valves prevent backflow Carries Lymph from tissue  lymph nodes  blood via thoracic duct –Fluid –Proteins –Ingested fats –Particulate matter –Antigen –Disease microorganisms –Cells (normal and cancerous)

15. 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. Trabecular Subcapsular

16. 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

17. Lymph Node Parenchyma Cortex –Primary, secondary nodules –B cells Deep cortex –(aka paracortex, juxtamedullary cortex, thymus dependent cortex) –No nodules –T cells Medullary cords –Plasma cells synthesize and release Abs into lymph flowing through the sinuses.

18. T-cell Zone Comprises of Deep Cortex and Paracortex Deep cortex: T and B cells enter from the circulation via HEV –Post capillary venules with high endothelial cells

19. Summary of Lymph Node flow Lymph Flow w/in Node Afferent Lymphatics  subcapsular sinus  trabecular sinuses  medullary sinus  efferent lymphatics

20. A B Question 2 C.Both D.Neither Q1) For the two pictures on the slide, select the correct answer for each of the below: Is encapsulated Contains germinal centers Peripheral lymphoid tissue Central lymphoid tissue

21. A B Question 2 C.Both D.Neither Q1) For the two pictures on the slide, select the correct answer for each of the below: Is encapsulated (B) Contains germinal centers (C) Peripheral lymphoid tissue (C) Central lymphoid tissue (D)

22. Question 3 The region inside the box contains which of the following upon antigenic stimulation: A.Plasma Cells B.Macrophages C.T-Cells D.Memory B-Cells E.All of the Above

23. Question 3 The region inside the box contains which of the following upon antigenic stimulation: A.Plasma Cells B.Macrophages C.T-Cells D.Memory B-Cells E.All of the Above