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Block 2 Week 1 > HIST - Lymphoid > Flashcards

HIST - Lymphoid Flashcards

1
Q

IMMUNITY

A
  • Innate (Natural)
    • Epithelia (physical barrier)
    • Phagocytic cells (macrophages and neutrophils)
    • Natural Killer Cells
    • Blood proteins; complement system
  • Adaptive (Acquired/Specific)
    • Humoral (Ab-mediated)
      • B cells and plasma cells
    • Cellular (Cell-mediated)
      • T cells
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2
Q

LYMPHOCYTES

A
  • B cells: respond to cell-free and plasma membrane bound Ag’s
  • T cells: respond to cell-bound Ag’s
  • Natural Killer Cells: T-like lymphocytes
    • Never enter the thymus, but are still immunocompetent
    • Lack TCR and CD4/CD8 coreceptor
    • Act non-specifically
    • Produce perforins and granuzymes
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3
Q

ACCESSORY CELLS

A
  • Macrophages: Antigen Presenting or Phagocytic
  • Dendritic cells: form the stroma of lymphatic tissues
  • Epithelial reticular cells: form the stroma of the thymus
  • Antigen Presenting Cells (APCs):
    • Mononuclear Phagocytes
      • Liver: Kupffer cell
      • Lung: alveolar macrophage
      • Brain: microglia
    • Express MHCI and MHCII on plasmolemma
    • Produce cytokines: interferon and interleukin
      • Force cells to enter mitosis
      • Chemotactic factors that recruit neutrophils and macrophages
    • Phagocytize, catabolize, process, present Ag
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4
Q

LYMPHOCYTES (5)

A
  • transplant cells
  • Originate in bone marrow; mature and differentiate in thymus
  • Found in T-dependent regions of the body:
    • Paracortical region of the lymph node
    • Periarteriolar lymphatic sheath in the spleen
  • Can differentiate between self and Ag
  • Naïve T-cells are immunocompetent but need to be activated by Ag into:
    • Memory T cells (adaptive immunity)
    • Effector T cells
      • Helper T cells (recognize foreign Ag)
      • Cytotoxic T cells (kill shit)
      • Suppressor T cells (suppress immune activity of other T-cells)
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5
Q

B LYMPHOCYTES

A
  • Ab-mediated Response
  • Originate and mature in bone marrow
  • Immunocompetent, but need to be activated by Ag from helper T cells
  • Activated B cells differentiate into:
    • Plasma cells
      • Primary response
      • Synthesize and secrete Ab’s
      • IgA, IgD, IgG, IgE, IgM
      • IgA is predominate in glandular tissue
      • IgG is predominate in serum
    • Memory B cells
      • Long term immunity
      • Form the mantle layer of the lymph node
  • Found everywhere in body, even a very few in the thymic medulla
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6
Q

IMMUNOGLOBULINS

A
  • IgA
    • Found in mucosa (attaches there to prevent getting degraded)
    • GI, GU, respiratory systems
  • IgD
    • Attaches to B-cells
  • IgG
    • Attaches to mast cells and basophils
    • Can enter placenta because it is small
    • Source of fetal immunity
  • IgE
    • Attaches to macrophages and neutrophils
  • IgM
    • Attaches to B cells
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7
Q

STROMA VS PARENCHYMA

A
  • Stroma: CT fiber scaffolding of an organ
  • Parenchyma: functional units/cells of an organ
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8
Q

FUNCTIONS OF THE LYMPHATIC SYSTEM (5)

A
  1. Concentration and elimination of Ag
  2. Production and maturation of lymphocytes
  3. Addition of Ab
  4. Provides way for tissue fluid to get back to blood stream
  5. Absorption of chylomicrons from small intestine and transport to liver/spleen
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9
Q

LYMPHOCYTES

A
  • Ab-independent differentiation in primary lymphatic organs
  • Ab-dependent activation in secondary lymphatic organs
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10
Q

LYMPHATIC ORGANS (7)

Derived from mesoderm!

A
  1. Diffuse lymphatic tissue
  2. Tonsils
  3. Lymph Nodes
  4. Spleen
  5. Thymus (1°) – derived from endoderm AND mesoderm
  6. Bone Marrow (1°)
  7. Fetal Liver (1°)
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11
Q

COMMON ELEMENTS OF LYMPHATIC ORGANS (4)

A
  1. Reticular fibers
  2. Dendritic cells (can act as APCs)
  3. Macrophages (phagocytic or nonphagocytic APC)
  4. Lymphatic vessels
    1. Thin, endothelium lines
    2. Some SM in larger vessels/thoracic duct
    3. Afferent (toward) and efferent (away)
    4. NO LYMPHATICS in avascular structures (hair, nails, cornea, cartilage), CNS, or bone marrow
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12
Q

DIFFUSE LYMPHATIC TISSUE

A
  • Found in all organs in contact with the outside world
    • Aka the lamina propria of mucosas
    • Digestive, genitourinary, respiratory organs
      • Peyer’s patches in ileum
  • M cells
    • Microfold/mucosal cells
    • Specialized, domed
    • APCs
  • B lymphocytes
    • Activated by Ag from M cells
      • Memory B cells
      • Plasma cells
      • Produce Ig, especially IgA
      • Lymph nodes –> thoracic duct –> circulation
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13
Q

LYMPHATIC NODULES

A
  • Basic structural unit of
    • Tonsils, spleen, lymph nodes, diffuse lymphatic tissue, and GALT/MALT/BALT (gut/mucosa/bronchial associated lymphatic tissue)
  • NOT found in Thymus
  • NO CT capsule
  • Make up Peyer’s patches in ileum
    • Huge lymphatic nodules that extend from LP into submucosa
  • Made up of B lymphocytes (few, if any, T lymphocytes)
    • B lymphoblasts
    • Plasma cells
    • Memory B cells
  • Primary nodule
    • No exposure to Ag
    • See in fetuses and neonates for the first few hours
  • Secondary nodule
    • Dark outside, lighter inside from mitotic cells
    • Have been exposed to Ag
    • Germinal centers of proliferating B lymphoblasts
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14
Q

TONSILS

A
  • Major tonsils (+ associated epithelium)
    • Nasopharygneal – Respiratory (pseudostratified ciliated columnar epithelium)
    • Lingual – Stratified squamous
    • Palatine – Stratified squamous
  • Other tonsils
    • Tubal tonsil
    • Lymphatic tissue of the soft palate
  • Form a circular band that protects the entrance to the GI and respiratory tracts called Waldeyer’s ring
  • No afferent vessels, only efferent
  • Incomplete CT capsule = protective barrier
    • Prevents leakage of Ag into the pharyngeal CT spaces
  • Tonsillectomy – usually no longer performed until 3 consecutive inflammations
    • Tonsils can sometimes grow back
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15
Q

LYMPH NODE

A
  • NOT a gland
  • In the course of lymph vessels, so acts as a lymph filter for lymphocytes entering the blood stream
  • Produces and maintains B and T cells
  • Paracortical region contains T-lymphocytes and APCs
  • Medullary cords contain macrophages and plasma cells
  • Cortex and Medulla
    • Afferent vessels
    • CT tissue capsule that extends inward as trabeculae
    • Hilus has entering arterioles and exiting venules and efferent lymphatics
      • Post-capillary venules are made of high endothelial cells that are spaces so lymphocytes can pass between them into circulation
    • Separated into the cortical and medullary regions
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16
Q

LYMPH NODE ANATOMY

A
17
Q

THYMUS

A
  • Endoderm (epithelial reticular cells) and mesoderm (lymphocytes)
  • 99% T-cells, no germinal centers
  • No afferent lymphatics
  • Maturation and differentiation of thymocytes
  • Bilobed and encapsulated
    • Lobes –> lobules: cortex and medulla
  • Grows until mid-teens (12-14) –> fat accumulation and involution
  • Stroma of epithelial reticular cells and some tingible macrophages
  • Epithelial reticular cells
    • Form blood-thymic barrier
    • Have desmosomes and tonofilaments
    • Produce the four hormones needed for T-cell maturation
18
Q

THYMIC CORTEX

A
  • Immunocompetency of T-cells: can recognize self and antigen
  • Phagocytize 98% of T-cells because they are intolerant
19
Q

THYMIC MEDULLA

A
  • Hassall’s corpuscles: whirls of old epithelial reticular cells
    • Very eosinophilic!
  • All thymocytes are immunocompetent
20
Q

BLOOD THYMIC BARRIER

A
  1. Capillary endothelium
  2. Capillary basal lamina
  3. Capillary CT sheath
  4. Basal lamina of epithelial reticular cells
  5. Epithelial reticular cells
21
Q

SPLEEN

A
  • Maybe the largest lymphatic organ in the body
  • Over a life-time, has the highest phagocytic capacity
  • Looks like cherry-cream cheese jello
  • Located in the left hypochondrium
    • Ribs that fracture above it can cause rupture
  • No afferent lymphatics
  • Surrounded by a fibromuscular CT sheath (subtype of dense regular CT)
    • Has some SM that allows it to contract
    • Trabeculae divide parenchyma into incomplete compartments
  • Functions:
    1. Immunological blood filter
    2. Phagocytize old and damaged RBCs
      1. No spleen, divert to liver, but too much so you see lots of wrinkly RBCs in smear
    3. Blood reservoir
    4. B and T cell proliferation
    5. Ab production (plasma cells)
22
Q

SPLENIC PULP

A
  • Parenchyma = splenic pulp
  • Red pulp = blood filter
    • Splenic sinusoids (capillaries that bubble, filled with RBCs)
    • Splenic cord (macrophage-sheath)
      • Cord of Billroth
      • Contains macrophages, lymphocytes, APCs, reticular fibers, some eosinophils
      • Macrophages –> APCs if an Ag from blood comes through and is phagocytized
  • White pulp = immunological filter
    • T-lymphocytes
    • Lymphatic nodules
    • Has eccentric arterioles covered by a periarteriolar lymphatic sheath that protects T-cells from seeing Ag in blood
      • Pushed from center after germinal center explosion on Ag presentation
23
Q

THEORIES OF RBC REMOVAL

A
  • Closed Circulation Theory
    • Macrophages have pseudopodia that extend into capillary and feel for old/damaged RBCs
    • Pull them out and phagocytize them in Cord of Billroth
  • Open Circulation Theory
    • Leaky capillaries allow blood to pool in cords
    • Macrophages phagocytize
  • In humans, both forms of circulation are seen

Block 2 Week 1 (8 decks)

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