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Cell Biololgy and Histology BAM > Final: Lecture 18 > Flashcards

Final: Lecture 18 Flashcards

0
Q

Acquired Immunity

A
  • Develops in response to antigens
  • More powerful than innate immunity
  • Takes longer to develop
  • Displays specificity and memory
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1
Q

Innate Immunity

A
  • Lacks immune specificty and memory, what you’re born with
  • Response = Inflammation
  • Neutrophils are the first responders
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2
Q

Lymphoid tissue

A

•Appears in body as a gradient from diffuse lymphoid tissue to aggregated lymphoid tissue to lymphoid organs

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3
Q

Passive immunity

A

•Temporary immunity due to dontated antibodies (i.e. transplacental passing of maternal antibodies to fetus)

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4
Q

Active immunity

A

•Long-lasting/permanent immunity due to self exposure to antigen resulting in memory T cells and B cells specific for antigen

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5
Q

Lymphoid organs

A
  • Primary: thymus and bone marrow

* Secondary: lymph nodes, spleen, tonsils

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6
Q

__________ originate in primary lymphoid organs and then take up residence in secondary lymphoid organs.

A

•Lymphocytes

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7
Q

Lyphopoiesis

A
  • All immune system cells originate in bone marrow
  • Immature T cells travel to thymus
  • B-cells travel to specific regions in lymphoid tissue
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8
Q

Antibodies (Immunoglobulins)

A
  • 5 classes: IgA, D, G, M, and E
  • Light and heavy chains
  • Highly variable regions: fab fragment, recognizes antigen
  • Less variable regions: Fc fragment, binds antibody to cells
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9
Q

IgA

A

•Found in saliva, milk, GU and respiratory tracts

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10
Q

IgD

A

•Found on surface of B cells traveling to lymphoid organs

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11
Q

IgG

A
  • Major Ig in blood

* Responsible for most antibody activity, only one capable of crossing the placenta

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12
Q

IgE

A

•Associated with allergic responses

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13
Q

IgM

A

•First antibody class expressed by developing B cells

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14
Q

B cells

A
  • Maturation involves the appearance of certain cell surface receptors
  • IgM and IgD, MHC class II proteins, complement receptors, Ig Fc receptors
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15
Q

Major Histocompatibility Complex

A
  • Function: Main function of MHC gene products is the presentation of antigenic peptides to T cells
  • MHC 1: Expressed on the surface of all cells except trophoblasts and RBC
  • MHC II: Expressed on the surface of B cells and antigen-presenting cells
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16
Q

CD8+ T cells recognize _____ _____ of foreign proteins bound to MHC class I on the surface of cells.

A
  • Peptide fragments
  • CD8 member of the Ig superfamily
  • Both the CD8 and T cell antigen receptor are required for the binding of MHC class I protein fragments
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17
Q

CD4+ T cells also recognize ____ ______ of foreign proteins bound to MHC class proteins on surface of ___.

A
  • Peptide fragments

* APCs

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18
Q

T cells

A
  • Pre-T cells develop in bone marrow
  • Travel to thymus and complete maturation
  • CD4+ T cells: recognize antigens bound to MHC class II molecules
  • Helper cells: assist CD8+ cell differentiation, assist B cell differentiation
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19
Q

CD8+ T cells

A
  • Cytolytic T cells (kills cells)
  • Bind to an antigen presenting cell, undergo mitosis
  • Release perforins and Fas ligand
  • Recognize antigens bound to MHC class I molecules
  • Mediators of cellular immunity
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20
Q

CD16+ T cells

A
  • Natural killer (NK) T cells
  • Activated (by tumor cell antigens) T-helper cells release cytokines: Interleukin-2, Interferon-gamma, Macrophage activating factor (MAF), chemotactic factor, tumor necrosis factor
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21
Q

Interleukin-2

A

•Stimulates proliferation of NK cells

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22
Q

Interferon-y

A

•Activates NK cells

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23
Q

MAF

A

•Activates macrophages

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24
Q

Tumor necrosis factor (TNF-ß)

A

•Kills tumor cells directly

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25
Q

T cells recognize _____ _____ only when they are presented bound to MHC.

A

•peptide antigens

26
Q

MHC restriction

A
  • Cytolytic T cells recognize an antigen presented by class I MHC molecules
  • Helper T cells recognize an antigen is association with class II MHC
27
Q

Foreign proteins are broken down into fragments, some of which have antigenic properties called ______.

A

•Epitopes

28
Q

Activated T cells undergo mitosis, some daughter cells become ______ cells, while others secrete _______.

A
  • Memory cells

* Interleukins

29
Q

B cells undergo mitosis, some daughter cells become ______ cells, while others become _______ cells.

A
  • Plasma, secrete appropriate antibodies

* Memory

30
Q

What is the role of Perforin?

A

•Pokes holes in cell membranes to kill the infected target cell

31
Q

The cytolytic T cells protects itself from perforin with _______.

A

•Protectin, binds to perforin

32
Q

___ _____, released by the cytolytic T cell and bound to the ___ receptor, together with granzye destroy by apoptosis the target cell.

A
  • Fas ligand

* Fas

33
Q

Complement system

A
  • Is an array of about 20 serum proteins which are synthesized in the liver and found in the blood
  • Facilitates inflammatory response
  • Either pathway involves coating the pathogen with complement initiating cascade
34
Q

Classic pathway

A

•Cascade is activated by antibody binding to a pathogen

35
Q

Alternate pathway

A

•Cascade is directly activated by the pathogen

36
Q

Activation Sequence

A
  • C1(the first complement factor in the cascade) is made up of three subcomponents.
  • Immunoglobulins bind to surface of pathogen
  • C1q binds to Fc region of Ig–>activates C1r–>activates C1s—>initiates complement cascade
37
Q

Activation Sequence after C1s

A
  • C1s–> C4–>C4a + C4b (binds to surface of pathogen)
  • C1s–>C2–>C2a + C2b
  • C2b binds to C4b–>C4b - 2b complex (=C3 convertase)
38
Q

Activation Sequence after formation of C3 convertase

A
  • C3 convertase–>C3–>C3a + C3b (most important opsonin)

* Multiple C3b bind to C3 convertase–>C4b - C2b - C3b complex (= C5 convertase) ** really attracts macrophages

39
Q

Activation Sequence after formation of C5 convertase

A
  • C5 binds to C3b–>C5a + C5b

* When C6, C7, and C8 are added to the complex, they form pores in the membrane of the pathogen. (KILL IT)

40
Q

The complement cascade results in the following:

A
  • activation of the membrane attack complex (MAC) on the pathogen leading to perforations and lysis
  • Production of opsonins, which are coatings that make the antigen more palatable to phagocytes
  • Release of chemotactic agents (chemokines) which attract phagocytes (chemotaxis) to the areas of infection or inflammation
41
Q

Parenchyma

A
  • Consists of the cells that typically pack areas of the lymphoid organ
  • Mostly lymphocytes
42
Q

Stroma

A

•Consists mostly of reticular fibers and cells, including undifferentiated cells and fixed and free macrophages

43
Q

Lymph follicles (nodules)

A
  • Gross structure: not encapsulated, cortex of dense, small lymphocytes, germinal center (only present if immune response is going on) of proliferative lymphocytes
  • Transient
  • Vascular supply: arteriole and venule supply the cortex, another supplies the center, lymph capillaries are not present
44
Q

Lymph node Hilus

A
  • Entry and exit point for vessels
  • Efferent lymphatic vessels as well as arteries and veins enter, carrying away from node
  • Afferent enter the convex side of the node
45
Q

Lymph node Capsule

A

•Dense collagen fibers, some elastic fibers and smooth muscle fibers

46
Q

Lymph node Cortex

A
  • Outer: contains lymph follicles (nodules)
  • Follicles: contain B cells, follicular/migrating dendritic cells, secondary (mantle and germinal center), and primary (lack mantle and germinal center)
  • Deep (inner): Contains Th cells, macrophages, high endothelial venuels (HEVs, port of entry for circulating differentiated lymphocytes to see lymph nodes)
47
Q

Lymph node Medulla

A
  • Irregular arrangement of loose medullary sinuses (lined with macrophages) and dense medullary cords (consist of blood vessels, lymphoblasts and plasma cells)
  • Site of lymphocyte reentry into lymph stream
  • Thymic-dependent areas in subcortical and deeper medullary regions, have primary T cells
48
Q

Thymus Histology

A
  • Capsule: blood vessels, no lymphatics
  • Septa: delicate CT
  • Most developed at puberty: 10-15 grams at birth, 30-40 at puberty
  • Involutes during adolescence, no lymph follicles, afferent lymph vessels, or lymph sinuses
49
Q

Thymus Cortex

A
  • Cortex (dark staining): small lymphocytes and immunoblasts
  • thymocytes migrate from cortical areas to medually
  • blood vessels surrounded by continuous epithelial barrier (allows to maintain lymphopoiesis while segregated from antigens)
50
Q

Thymus Medulla

A
  • Light staining, specialized to allow entry channel into blood stream of differentiating lymphocytes
  • Capillary beds are not sheathed by epithelial cells
  • Hassall’s corpuscles: whorls of highly keratinized medullary epithelial cells, produce cytokine thymic stomal lymphopoietin
  • Stimulates thymic dendritic cells needed for the maturation of single positive T cells
51
Q

Differentiation of T cells**

A
  • Double negative
  • Double positive T cells move to outer cortex
  • Single positive move to inner cortex: express TCR receptors and either CD4 or CD8 coreceptors
52
Q

Double negative T cells

A
  • Lack cell surface molecules typical of mature T cells
  • Enter cortex from blood vessels
  • Proliferate in subcapsular area*
53
Q

Double positive T cells

A
  • Move to outer cortex
  • Confronted with epithelial cells with cell surface MHC classes I and II for clonal selection (if you aren’t good enough, they will kill you!!!)
  • Express both CD4 and CD* coreceptors and TCR receptors
54
Q

Spleen Morphology

A
  • 5.6 x 4 inches, no lymph sinuses or afferent lymph vessels
  • Covered by peritoneum except at hilus
  • Blood vessels enter and leave hilus
55
Q

Spleen Functions

A
  • Only lymphatic organ specialized to filter blood
  • Stores and removes worn-out RBCs
  • Recycles iron
  • Converts hemoglobin to bilirubin
  • blood formation in the fetus
56
Q

Spleen Immunologic functions

A
  • Sreens foreign material in the blood
  • Produces lymphocytes and plasma cells (produced in bone marrow, activated by spleen)
  • Removal leads to overwhelming bacterial infections in infants, children, and young adults
57
Q

Spleen Histology

A
  • Capsule: thin, dense fibrous CT with elastic fiber and some smooth muscle
  • Trabeculae: extend inward from capsule, covered by mesothelium
58
Q

Spleen Parenchyma

A
  • B cells located in the peripheral white pulp, often have germinal centers
  • T cells found in the areas surrounding the central artery near the center of white pulp
  • Reticular fibers are associated with fixed macrophages and support splenic pulp
59
Q

Spleen White Pulp

A
  • Elongated, branched strands always associated with arteries
  • Zones of diffuse lymphoid tissue and germinal centers (contain B cells)
  • Lymph follicles, chief site of lymphocyte production
  • T-cell areas surround follicles and periarteriolar sheaths (PALS)
60
Q

Spleen Red Pulp

A
  • Surrounds white, contains large number of RBCs

* Cords of lymphoblasts and plasma cells = Billroth cords

61
Q

Spleen Vascularization

A
  • Arteries: splenic enters at hilus, trabecular arteries branch off
  • Central arteries: adventitia (CT) loosens and becomes mesh-like reticulum infiltrated with lymphocytes
  • After capillaries form, supplying white pulp, central arteries lose their white pulp investment and enter red pulp to form penicillus
62
Q

Penicillus

A
  • composed of pulp arteriole, sheathed arteriole, and terminal capillary
  • Terminal cap. drains into intercellular spaces (open system) or venous sinuses lined with reticuloendothelial cells (closed system)

Cell Biololgy and Histology BAM (11 decks)

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