= Lymphatic systems =

Transcription

1 = Lymphatic systems = Why do we need it? Lymph node Lymphatic vessel Lymphatic vessel Vein Capillary Artery tissues blood Capillaries Speaker: 許書豪解剖學科助理教授 1

2 Lymphatic tissue and organ Lymphatic organs/tissues Diffuse lymphatic tissues Or celled MALT: mucosa-associated lymphatic tissue Dispersed lymphocytes in lamina propria of mucosa. Tosils(Palatine, Lingual, Pharyngeal) GALT: gut-associated lymphatic tissue (Peyer s patches, vermiform appendix, etc) BALT: bronchus-associated lymphatic tissue NALT, LALT, D-MALT..etc. Lymph node Thymus Spleen Bone marrow Components Reticular framework: (fibroblastic) reticular fibers & cells Free cells: T-& B-cells, NK cells, macrophage (APC) Immune response 2

3 Immune Responses Protective surface mechanisms Physical barrier skin, mucosa, Chemical defense low ph Various secretory substances (thiocyanate, lysozymes, interferon, fibronectin) Nonspecific (Innate) Complements Phagocytic cells (macrophage, neutrophils, monocytes) Natural killer (NK) cells Specific (adaptive) Humoral response (mainly B-lymphocytes) Cell mediated response (T-lymphocytes) 3

4 Lymphocytes Where are they? 70 %: Circulating poolof immunocompetent cells in systemic circulation long-lived, mature lymphocytes (mainly T-cells) 30%, specific tissues mainly short-lived, immature or activated cells destined for a specific tissue. In the connective tissue (lamina propria) of respiratory, gastrointestinal, and urogenital tracts 4

5 Classifications of immune cells Centrifugation: White blood cells. Hematopoiesis: lymphoid lineage: B-, T- cells Myeloid lineage: phagocytic cells (monocyte, eosinophil, basophil) Erythroid/megakaryocyte lineage: red blood cells, megakaryocytes Surface markers: Cluster of differentiation (CD) molecules (e.g., CD4+ T cells.) 5

6 Discovery of 2-cell model: B-and T-lymphocytes Jacques Miller, Lancet, 1962: mice lacking a thymus did not make antibodies (Abs) -producing cells in response to immunization. Bruce Glick, JEBMS, 1965: Removal of Bursa of Fabricus impaired bird s ability to produce Abs. Henry Claman, JEM, 1966: Irradiated mice given bone marrow cells+ thymus cells produced more Abs than those given either cell type alone. Jacques Miller, JEM, 1968: depletion of thymus cells had very little effect on Abs production, whereas depletion of bone marrow cells completely eliminated the Abs production. Jacques Miller (1931- )

7 Target: Antigen Presenting Cells (APC) 1. APCs take up foreign material, process antigen and present processed antigen to appropriate lymphocytes. 2. Characterize with numerous long branching cytoplasmic processes and contain phagolysosomes. Interdigitating dendritic cells of spleen & lymph node; Type 2 & 3 epithelioreticular cells of thymus; Macrophages Langerhans cells of skin; 3. Many other cells types also play roles of APC, such as B- lymphocytes, endothelial cells, dermal fibroblasts, thyroid epithelial cells, and astrocytes. 7

8 B-lymphocytes Location: 20-30% of circulation pool B is named after bursa of Fabricius in birds, but kept later for bone marrow derived cells in mammal Maturein bone marrow Function: Participate in humoral response Derive into plasma cells Make and secrete antibodies (Ig, immunoglobulin, e.g. IgG) 1. Circulating antibodies 2. Membrane bound antibodies (becomes BCRs) Surface markers B-cell receptors (BCRs) Major histocompatibility complex II (MHCII) CD markers: CD9, 19, 20, 24 8

9 Location: - 70% of circulation pool - Maturein thymus Functions: T-Lymphocytes - Participate in Cell-mediated response Surface markers: T-cell receptors (TCRs) CD markers:cd2, CD3, CD7. 9

10 Different types of T-lymphocytes Helper T-cells (CD4 + ): TH1 cell (IL-2, IFN-γ, TNF-α) interact with CD8+ T-cells, macrophages, NK cells to induce cell mediated response TH2 (IL-4, IL-5, IL-10, IL-13) interact with B-cells to induce humoral response Cytotoxic T-cells (CD8 + ): kill virus infected, cancer-transformed, transplanted cells via cell mediated response Memory T-cells Suppressor T-cells Gamma/delta (γ/δ) T-cell neither CD8 + nor CD4 + ; Do NOT recirculate between blood and lymphatic organs 10

11 Natural Killer cells Location: 5-10% of circulating pool. They DO NOT mature in Thymus Functions: Antibody-dependent cell-mediated cytotoxicity (ADCC): Recognize and kill target cells bound by antibodies Recognize the virus-infected or tumor transformed cells. Generate perforins and granzymes (fragmentins) that create channels on the plasma membrane and induce apoptosis Cancer cell Surface markers: CD16, CD56, CD94, IFNγ-R, Fc-R NK 11

12 Cell mediated response Cytotoxic T cells recognize antigen (through MHC-I)-presenting cells Undergo clonal expansion Secrete perforins and granzymes Kill targets by creating channels on the plasma membrane and induce apoptosis Humoral response Helper T cells recognize antigen (through MHC-II)-presenting cells secrete cytokines to activate other immune cells undergo clonal expansion activate B cells that have encountered antigen (Two signals). B cells undergo clonal expansion. Some differentiate into plasma cells. Generate tons of antibodies Antibodies bind to antigen to form Ab-Ag complex Pathogen with this Ab-Ag complex will be destroyed by: NK cells, macrophages, eosinophils + You will learn more in immunology! 12

13 Lymphatic tissues/organs Primary (central) lymphatic organs bone marrow, GALT, thymus cells undergo antigen-independentproliferation and differentiation (immunocompetent cells). Secondary (peripheral) lymphatic tissue/organs effector tissue/organ lymphatic nodule, lymphatic node, tonsils, spleen T-and B-cells undergo antigen-dependentactivation into effector lymphocytes and memory cells. 13

14 Lymph Node Functions: 1.Filtration of Lymph elimination of noxious and foreign substance from lymph 2.Production of Lymphocytes 3.Phagocytosis sinus, nodules and cord, macrophages 4.Antigen-antibody reaction (germinal center) T- & B-cells 5.Antibody formation (B-cell = plasma cell, medullary cord) 14

15 Stroma Histology of Lymph Node capsule (lack at hilum), trabeculae, (dense c.t.) reticular tissue reticular cells and reticular fibers Parenchyma (lymphatic tissue proper) cortex: - superficial cortex or nodular cortex, lymphatic follicle (nodule), trabecular - deep cortex or paracortex - lymph sinus subcapsular, medulla- medullary cord, medullary sinus 15

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18 Hilum region artery, vein and efferent lymphatic vessel pass through. 18

19 Reticulin fiber staining Subcapsular sinus (SS): First sinus following afferent lymphatic vessel Macrophages /Epithelial cells TS: trabecular sinus CS: cortical sinus MS: medullary sinus 19

20 S S S PF S S S Primary lymphatic follicle (PF): no germinal center (naïve B-cells) Secondary lymphatic follicle (SF): germinal center +mantle zone (activated B-cells) 20

21 Distribution of B-cells (CD20+) Types of B-cells in secondary follicle Germinal center: Dark zone: B-cells (centroblast) under proliferation (Ki67+) Light zone: B-cells (centrocyte) under selection Mantle zone: Senescent B-cells Q: What information is provided in each staining? Ki67:proliferation ASH Education Book January 1, 2007 vol no

22 Centrocyte & centroblast (Both B-cells) Tinglible-body Macrophage CC CC CB CB CB M Resting B-Lymphocytes Plasma cells (arrows) 22

23 Distribution of T-cells (CD3+) Where are T-cells? Few in follicles (T H ); Most in paracortex H&E P=paracortex

24 Follicular dendritic cells (FDC) : Coach of B- cells mesenchymal origin; usually found in germinal centers (superficial cortex). Anti-CD21 supporting follicle are NOT antigen presenting cells (APC), because they lack of MHC II. 24 Yellow circle: Germinal center H&E antigen-antibody complexadheres to dendritic cell process by means of Fc receptor. Don t mess up with (Interdigitating) dendritic cells, which are hematopoietic origin, located in the T-cell rich areas (paracortex). antigen-presenting cells (APC)

25 plasma cells: B-cells derived Golgi apparatus (Clear region in cytoplasm) massive Ab production Clock-face, eccentric pericenter nucleus 25

26 Secondary lymphatic follicle (nodule): B-cell training camp Training schedule 1. Entry into GC from sinus 2. Proliferate (clonal expansion) 3. Affinity selection by FDC 4. Class switching by Helper T cells 5. Differentiate into Memory B cells/plasma cells 6. Plasma cells secrete antibodies to label targets carrying antigen. Heesters et al. Nature Reviews Immunology 26 14, (2014)

27 Subcapsular sinus endothelial cells with gaps, no basal lamina, contains reticular cells, reticular fibers, macrophages,. lymphocytes, plasma cells, 27

28 Reticular fibers (Fibroblastic) Reticular cell Derived from mesoderm Different from epithelioreticular cells in thymus 28

29 Medulla: sinus (MS) and cord (MC); contains lymphocyte, (fibroblastic) reticular cells, macrophages 29

30 Circulation of lymphocytes Lymphocytes migrate from artery HEVparacortex lymph sinus Efferent lymphatics thoracic duct back to vein. Efferent lymph clear, and more lymphocytes (T & B, plasma cells) Afferent lymph particulate & soluble antigen; relatively few lymphocyte, APC 30

31 High endothelial venules (HEV): Specialized post-capillary venules in all secondary lymphoid organ except spleen. (why special?) Located in deep cortex Cuboidal endothelial cells Extravasation 31

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33 Thymus: T-cells training camp Functions: 1.Development of immunocompetent T-cells 2.Clonal expansion of mature naïve T-cells 3.Development of immunological self-tolerance 4.Secretion of hormones and other regulating factors Thymulin, thymopoietin, α1- &β-4 thymosin Effect of thymectomy in newborn mice: death within 3 month No development for immune mechanism No development for other lymphatic organs No tissue graft rejection 33

34 Stroma Capsule, Septae (trabeculae) Histology of Thymus (lymphoepithelial organ) Parenchyma thymic lobules (thymic tissue proper) Cortex Cortico- medullary junction Medulla Hassal s corpuscle lymphocytes (thymocytes), epithelioreticular cells, blood thymic barrier, Macrophages, 34

35 Cortex -- only capillaries; Blood-Thymus barrier Medulla Hassal s corpuscle No sinus (how to distinguish medulla?); no afferent, but only efferent lymphatics Septae separate each thymic lobules 35

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37 Thymic parenchyma contains: Epithelioreticular cell (ERC) (arrows, right) cells with large eosinophilic stained cytoplasm NOT (fibroblastic) reticular cells!!! Endoderm derived (third pharyngeal pouch) NO reticular fibers!! Developing T lymphocytes cells with large basophilic stained nucleus 37

38 Post-capillary venule Medulla Cortico-medullary junction Cortex capillary arcuate connection Epithelioreticular cell efferent lymphatics arteriole venule 38

39 Epithelioreticular cells (ERC) Type 1-6, also called thymic nurse cells Joined each other by desmosomes Rich of tonofilaments (or called keratin intermediate filaments) immunoperoxidase antiantikeratin Ab epithelioreticular cells 39

40 T-cells training: 1.Hematopoietic stem cells enter from post-capillary venules (PCV) in medulla 2.Positive selection by ERC type 2 and 3 3.Negative selection by ERC type 5 4.Differentiate into cytotoxic (CD8+) and helper (CD4+) T cells. 5.Leave through PCV. ERC type 1: barrier between cortex and capsule ERC type 4: Cortico- medullary junction

41 ERC type 6 Keratinized epithelial cells. forms Hassall s corpuscle. Produce IL-4, IL-7 to promote thymic differentiation of T-cell education. Quick summary of ERC Cortex: Medulla type 1,2,3 type 4,5,6 Red: involved in T-cell education

42 Blood-Thymus barrier Epitheiloreticular cell layer: ERC type I Basal lamina Perivascular c.t.: Macrophage Capillary wall: Pericytes Basal lamina Endothelial cells Each compartment is joined by tight junction 42

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44 1. age Involution accidental involution

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