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Histology- Immune System
 

Histology- Immune System

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    Histology- Immune System Histology- Immune System Presentation Transcript

    • Borela, Vandon T.Brigola, Jessica Luz M.Tenchavez, Jeanne Marie Gabrielle C.
    • A functional system A functional systemthat has the ability to that has the ability todistinguish “self” distinguish “self”from “non-self”. from “non-self”.It includes all organs It includes all organsand structures that and structures thathave lymphoid have lymphoidtissue as parenchyma. tissue as parenchyma.
    • Immune cellsdevelop in theprimary organs-- bone marrow andthymus (Yellow)Immune responsesoccur in thesecondary organs(Blue)
    • 1. ProtectiveSurfaceMechanisms2. Non-specificTissue Defense3. Specific ImmuneResponses Cell-mediated immunity Humoral immunity
    • These are defenses that the body uses nomatter what the invader may be.These defenses are:
    • These are defenses that the body uses nomatter what the invader may be.These defenses are:
    • These are defenses that the body uses nomatter what the invader may be.These defenses are:
    • These are defenses that the body uses nomatter what the invader may be.These defenses are:
    • These are defenses that the body uses forspecific invaders.These defenses include:a. The production of Antibodies.b. The killing of specifically infected body cells and
    • CELLS OF THE IMMUNESYSTEM
    • Lymphocytes in peripheral blood smearThese are B and T-cells that have undergone antigen-INDEPENDENT differentiation and are traffickingthrough the bloodstream on their way to lymphoidorgans/tissue.
    • Diapedesis: it’s not just for the Normans and the Saxons… Cytokines and chemokines (along with selectins and integrins) mediate EXTRAvasation of lymphocytes into tissues. Tether Roll Arrest Migrate blood flow cytokines chemokines L. Stoolman APCs and other cells
    • Natural Killer (NK) Cells They are able to kill virus- infected cells by inducing apoptosis by a mechanism which is not antigen-specific
    • • Derived from precursors in the bone marrow and also mature there During the Division of B cellsTwo new cell types arecreated: 1. plasma cells 2. B memory cells
    • Plasma Cells are mature B lymphocytes White arrows = Golgi regions
    • Memory CellsThese cells have a prolonged life span and can thereby "remember" specific intruders
    • Immunoglobulins
    • T Lymphocytes •Migrates from the bone marrow to the thymus where they develop into mature T (thymus- dependent) lymphocytes.
    • Functional Subset of T Lymphocytes : 1. T helper cells (TH cells) 2. Cytotoxic Cells (Tc cells)3. Suppressor T cells (Ts cells)
    • T helper cellsIt helps other lymphocytes to perform their effector functions by secreting a variety of locally acting mediators known as cytokines
    • Cytotoxic T cellsIt kills virus-infected and malignant cellsThey require interaction with TH cells to become activated and proliferate to form clones of effector cells.
    • Suppressor T cellsThe functional subset of this cell is still controversialIt can be demonstrated by CD8- bearing lymphocytes in experimental animals
    • Major Histocompatibility Complex(MHC)group of genes that code for proteins found on the surfaces of cells that help the immune system recognize foreign substances.
    • Antigen-Presenting Cells(APCs)Specialized white blood cells that help fight off foreign substances that enter the body
    • Types of APC: 1) Macrophages 2) Dendritic cells 3) B cells
    • Macrophagescontinuously phagocytose self- proteins and cells in their vicinity, during normal tissue repair and aging (e.g. old red blood cells)
    • Dendritic cellsmostly found in the skin and mucosal epithelium, where they are referred to as Langerhans cells.
    • B cellsLeast efficient antigen presenting cellsthey possess specific antigen receptors, surface immunoglobulinsB cells present antigen via MHC-II
    • LYMPHOID TISSUES
    • Lymphoid tissue is connective tissuecharacterized by a rich supply of lymphocytes.Lymphoid tissue exists in two forms: 1. Loose or diffuse lymphoid tissue 2. Dense Lymphoid tissue Non-nodular dense lymphoid tissue Nodular dense lymphoid tissue
    • LYMPHOCYTES IN CONNECTIVE TISSUE: MALT = mucosa-associated lymphoid tissue LN Ross and Pawlina, Histology: A Text and Atlas U-M Histology CollectionDiffuse lymphoid tissue Primary lymphatic nodule/follicle (LN)
    • LYMPHOID ORGANS
    • • T-cell education• Self vs. nonselfdistinctions• Cell-mediatedimmune functions• Populates effectororgans Lymph nodes Lymphatic nodules Spleen Tonsils
    • The Thymus undergoes a process called THYMIC INVOLUTION, as T cells leave the thymus to populate other lymphoid effector organs, the organ shrinks, leaving only the epithelioretucular cellsThe young thymus Thymus at puberty
    • High magnification view of medulla T-cells that survive selection process allowed to cross venule endothelium (INTRAvasation) to enter circulation.
    • Tonsils: MALT of the oropharynx
    • TONSILSThe palatine tonsils are paired structures made ofdense accumulations of lymphatic tissue located in themucous membrane of the junction of the oropharynxand oral cavity.
    • Wanderlust:lymphocytes don’t just stay in one placeFrom the MALT, lymphocytes can squeeze into lymph vessels…
    • ..go through larger lymphatic channels in themesentery…
    • ..and end up at a LYMPH NODE.
    • Lymph Nodes Main functions:1. Filter lymph, thereby promoting lymphocyte contact with antigen2. Provides necessary microenvironment for antigen- dependent differentiation.
    • Lymphoid circulation in the body takes place in boththe blood stream and the lymphatic vessels, aseparate vessel system that carries cells of thelymphoid system andtheir products (cytokines, antibodies, etc.).
    • Lymphatic Circulation Through a LymphNode Lymph nodes filter lymph 1. Afferent lymphatic vessels drain lymph into the Subcapsular Sinus 2. Lymph then passes to the Trabecular sinuses 3. From there, the lymph goes to the Medullary sinuses. 4. Lymphocytes and macrophages pass easily between these sinuses and the tissue of the lymph node. 5. Macrophages in sinuses monitor the fluids. Macs phagocytose the antigenic material and present it to T- and B-cells
    • Lymph Node Structure-Capsule & subcapsular sinus- Trabeculae & trabecular sinuses sinuses contain lymph, macrophages, and reticular cells- Cortex: •superficial cortex (B-cells) -primary follicles/nodules -secondary follicles/nodules- Medulla: • medullary cords (B-cells, plasma cells) • medullary sinuses (lymph, more macrophages, plasma cells, and reticular cells)
    • Blood Circulation Through a Lymph Node 1. Blood enters through an artery at the hilus 2. Arterioles branch from hilar artery to feed into capillary beds 3. Capillary beds are drained by high endothelial venules 4. HEVs drain into hilar vein
    • Filters the bloodDestroys old red blood cellsServes as an immune organDivided into Red Pulp(RBC/hemoglobin recycling)White Pulp (responsible forimmune functions)
    • Immune Functions of the Spleen • Monitoring antigens in blood • Proliferation of lymphocytes • Production of humoral antibodies • Formation of blood cells in fetal lifeHematopoietic • Removal and destruction of RBCs &Functions plateletsOf the Spleen • Retrieval of iron from RBC hemoglobin • Storage of RBCs and platelets (more so in non-human species)
    • Spleen: Anatomy
    • Organization of the spleen: white pulp and red pulpWhite pulp: lymphatic aggregations around “central” arteries: periarterial lymphatic sheath (PALS): T-cells lymph nodules: B-cellsRed pulp: cords and sinuses
    • PALS w/ secondary follicleShown here with “central”artery cut in cross section –note that the CA has beenpushed off to the side by therapid expansion of cells inthe germinal center (GC)RP= red pulpMZ= marginal zone (antigenpresentation)dashed circle = T-cell richzone
    • Spleen (red pulp)at high power (40x) sinus cord cord sinus
    • Here, you are insidethe sinus lookingthrough to the cord,where both amacrophage (M) anda neutrophil (N) areoutside the sinus.Note that theendothelial cells havea rodlike appearance.
    • A B A. red pulp B. higher mag of venousC sinus and cords of Billroth C. silver-stained section D. diagram
    • redpulp white pulp