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CPR 2 > Cells Of Lymphatics > Flashcards

Cells Of Lymphatics Flashcards

1
Q

What is the function of the lymphatic system?

A

Function:

  • monitor body surfaces and interstitial fluid compartments
  • Removal of excessive interstitial fluid
  • Provides defense mechanisms
  • production of immune cells (lymphocytes, monocytes, plasma cells)
  • fatty acid absorption and transport of fat, chyle to general circulation

Basis for this self defense- enable the body to distinguish self from non self
-carried out by-cells, effector molecules, tissues and organs

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2
Q

What are GHRH organs of the lymphatic system?

A

Primary- bone marrow, thymus

Secondary - spleen, tonsils, lymph nodes, diffuse lymphatic tissue, lymphatic nodules

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3
Q

What are the cells of the lymphatic tissue?

A

Principal effector cells

Support cells

Specialized epithelial and stromal cells

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4
Q

What are the principal effector cells?

A

Lymphocytes, B cells, T cells, natural killer

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5
Q

What are the support cells?

A

Monocytes, macrophages, neutrophils, basophils, eosinophils, dendritic cells, follicular dendritic cells

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6
Q

What are the specialized epithelial and stromal cells?

A

Reticular cells, langerhans, epithelioreticular cells

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7
Q

Summarize lymphocytes

A
  • non terminally differentiated cells
  • responsible for immunologic. Surveillance
  • 60-80%, mainly long lived, mature T cells, circulating pool of immunocompetent cells
  • 30% short lived, immature, or activated but destined for specific tissue (connective tissue, epithelia)
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8
Q

What are the characteristics of T lymphocytes?

A

Differentiate in the thymus

Long lived, cell mediated immunity, 60-80% of lymphocytes

Secrete cytokines when activated
-cytokines affect the function of effector cellls (T & B, monocytes, macrophages, APCs)

Express- CD2, CD3, CD5, CD7, CD28, CD40L

T cell receptors (TCR)- recognize antigen attached to identification molecules (MHC molecules)

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9
Q

What are the subclasses of T lymphocytes?

A

-T helper cells (Th1, Th2)
TH cells recognize antigens presented by antigen presenting cells (APCs)
Express CD4, in addition to those mentioned above

  • Cytotoxic lymphocytes (CTL) - “patrols”
    • CTLs - recognize antigens presented on cancer or viral infected cells
    • CTLs- express CD8, in addition to those mentioned above
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10
Q

How are TH cells activated ?

A

I) first signal, when they interact with MHC-Ag complex
II) Costimulatory signal, between T cell and APC

Synthesize interleukins (CD4+ cytokines which stimulate differentiation and proliferation of T, B, & NK cells)

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11
Q

What are the functions of TH1 cells?

A

Recognize Ag presented by APCs

Synthesize- IL2, IFN-y, TNF-a-

Interact with cytotoxic lymphocytes, cells and macrophages to control intracellular pathogens

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12
Q

Whaat are the functions of TH2 cells?

A

Recognize Ag presented by APCs

Synthesize IL4, IL5, IL10, IL13

interact with B lymphocytes to initiate antibody mediated immune response for extracellular pathogens

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13
Q

Whaat is the function of CD8+ lymphocytes?

A

Express CD8, Kill target cells - cancer cells, viral infected cells, parasites, transplanted cells, cells infected with intracellular microorganism

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14
Q

What is the cell mediated immune response of CD8 T cells?

A

Destruction of a transformed or virus infected cell by cytotoxic CD8+ T lymphocyte

Activation: TCR binds the MHC 1-Ag complex on target cell

-Clonal expansion:cell division and differentiation into killer cells

Killer cells: performing (perforate cells), granzymes (activate caspases-cell apoptosis), granulysin

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15
Q

What are the functions of regulator (suppressor) T lymphocytes?

A

Suppress the immune , response to self and foreign antigens by influencing other cells of

- CD4+ cells that co-express CD25+ and FOXP3
- Secrete IL10, TGF-B
- delayed hypersensitivity reaction (type IV)
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16
Q

What is the function of gamma/delta T lymphocytes?

A

Develop in thymus

Reside and form first line of defense in epithelia

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17
Q

What are MAIT lymphocytes?

A

Mucosa invariant T lymphocytes

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18
Q

How much of circulating lymphocytes natural Killer cells?

A

5-10% of circulating lymphocytes

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19
Q

Describe natural killer cells

A
  • Neither B nor T lymphocytes but share same line of development
  • Innate immunity
  • Programmed to kill target cells similar in fashion to CTL method
  • Enzymes released: granzymes and perforins
  • CD markers- CD16, CD56, CD94
  • Express Fc receptors-recognize the Fc region of antibodies coating target cells
  • NK associated lysis of cells coated by antibodies (IgG) or complement (C3)- (antibody dependent cell-mediated cytotoxicity, ADCC)
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20
Q

Describe B lymphocytes

A
  • differentiate in bursa equivalent organs
  • participate in humoral immunity
  • variable life span
  • express antigen binding site, B cell receptor (BCR) and MHC II on their surface

CD markers: CD9, CD19, CD20, CD40

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21
Q

Whaat are the subtypes of B cells?

A

Plasma cells: production and secretion of antibodies (immunoglobins, Ig)

Memory B cells: respond to second encounter with the same antigen

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22
Q

Explain the activation of B lymphocyte

A

I) first signal, when they interact antigen- BCR-Ag compl3x

- Antigen is engulfed by B cell
- Antigen-antibody(Ag-Ab) complex is eliminated by NK cell destruction, phagocytosis by macrophages or eosinophils

II) Costimulatory signal-, between the B cell and TCR on Th cell.
T cell secrete cytokines to stimulate B cell differentiation and proliferation

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23
Q

What is the mononuclear phagocytic system?

A
  • perisinusoidal macrophages (kupfer cells)
  • Langerhans cells (skin)
  • dendritic cells (spleen, lymph nodes)
  • macrophages)
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24
Q

What is non-mononuclear phagocytic system?

A

B lymphocytes

Epitheliorecticular cells (thymus)

Epitheliorecticular cells (II, III)

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25
Q

What are the mechanisms of macrophages?

A

Presented antigens to B and T cells

Partially degrade both proteins and polysaccharides

Digest pathogenic microorganism through lysosomal action in combination with CD4+ T lymphocytes

  • secrete multiple cytokines (lymphokines, complement components, interleukins) and enzymes (proteases, hydrolases, lipases)
  • sequestration and removal of foreign materials and organisms that remain undigested or have not provoked an immune response
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26
Q

What is special about macrophage 1- M1?

A

Activated by IFN-y

  • avidly phagocytic- lyse ingested pathogens and fireign antibodies
  • promote inflammatio, ECM damage and apoptosis

-

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27
Q

What is special about macrophage 2(M2)?

A

Activated by interleukins

Downregulate inflammation

Promotes rebuilding of ECM and cellular proliferation

Stimulates angiogenesis

28
Q

What is antigen presentation?

A

Antigen processing and presentation on its surface of APC

  • endocytosis of antigen and binding to MHV II molecules in endosomes
  • Translocation to the plasma me,Braine

Interaction with CD4+ cells

29
Q

How do T cells interact with endogenous antigens?

A
  1. Antigen proteosome degradation
  2. Formation of Ag-MHC complex (rER)
  3. Translocation of complex via Golgi
  4. Presentation of Ag-MHC-1 on plasma membrane followed by CD8 recognition (CTL)
30
Q

How do T cells interact with exogenous antigens?

A
  1. MHC-II assembly in rER
  2. Translocation of MHC-II to membrane
  3. MHC-II displayed on cell surface
  4. Endosomal endocytosis of MHC-II
  5. Exogenous Ag endocytosis
  6. Proteolytic degradation of Ag
  7. Formation of Ag- MHC-II complex
  8. Display of Ag.-MHCII complex on cell surface followed by CD4+ T helper recognition
  9. Lysosomal degradation of failed of Ag-MHC-II recognition
31
Q

What is an innate response?

A

Nonspecific immunity

Occurs through action of neutrophils, macrophages, mast cells and NK cells

Fast and nonspecific

Does not produce memory cells

32
Q

What are adaptive immune responses?

A

Specific immunity

Depends on initial recognition of antigens by B and T cells

Slower and specific

Produces memory cells

  • primary response
  • secondary response
33
Q

What is antibody mediated immunity?

A

Helper T cells, B-cells and plasma cells

-cause a release of antibodies that act on invading antigen

34
Q

What is cell mediated immunity?

A
  • Specific T cells that specialize in cytotoxicity

- Granzymes and perforins

35
Q

What are the types of lymphoid tissue?

A

-Diffuse lymphoid tissue

  • Nodular lymphoid tissue
    • solitary nodules
    • aggregate nodules
36
Q

What are the lymphoid organs?

A

Primary lymphoid organs

  • bone marrow
  • thymus
  • GALT

Secondary lymphoid organs

  • lymph nodes
  • spleen
  • tonsils
37
Q

Describe diffuse lymphoid tissue

A
  • non encapsulated accumulations of lymphocytes and other free cells (plasma cells, eosinophils, fibroblasts)
  • protects the body from antigens
  • initial immune response
  • located in the Lamina propria (subepithelial tissue)
  • Mucosa Associated Lymphatic Tissye (MALT)
38
Q

What are the cells in a lymphatic nodule?

A
  • Lymphocytes
  • Reticular cells
  • Dendritic follicular cells
  • Macrophages
  • Follicular dendritic cells
39
Q

Whaat is the purpose of lymphocytes in lymphatic nodules?

A

B lymphocytes

Activated > proliferate> plasma cells & memory cells

40
Q

What do reticular cells do in lymphatic nodules?

A

Produce reticular fibers (stroma)

41
Q

What do dendritic follicular cells do in lymphatic nodules?

A

Most efficient APCs

PResent antigens on MHC I & MHC II molecules

42
Q

What are the functions of macrophages in the lymphatic nodules?

A

Phagocytic & APC (contain MHC I & II molecules)

43
Q

What are the purposes of follicular dendritic cells?

A

Dendritic in nature: lack MHC-II molecules: harbors Ag-Ab complexes

44
Q

What are the characteristics of lymphatic nodules?

A

-localized concentrations of lymphatics and other free radicals (plasma cells, eosinophils, fibroblasts)

Located in the wall, of the GI ttact (tonsils, ileum), respiratory, genitourinary

  • Nonencapsulated, solitary(duodenum) or aggregated (tonsils, peyers patches)
  • protects the body from antigens
  • Mucosa associated lymph tissue (BALT, GALT)
45
Q

What are the classifications of lymph nodules/follicles?

A

Primary

Secondary

46
Q

What are primary lymph nodules/follicles?

A

Mainly small lymphocytes

Dense heterochromatin

47
Q

What are secondary lymph nodules/follicles?

A

After exposure to antigen

48
Q

What is the germinal center of the lymphoid nodule/follicle?

A

Center of lymphocyte activation proliferation and differentiation

  • pale staining central region
  • large immature lymphocytes with dispersed heterochromatin
  • follicular dendritic cells and macrophages
49
Q

What is the mantle zone or corona of the lymphoid nodule/follicle?

A

Outer dark staining region, with smaller cells

50
Q

Where is the thymus located?

A

Superior mediastinum

51
Q

What are the characteristics of the thymus?

A

Primary lymphoid organ

No afferent lymphatics

Origin- mainly 3rd pharyngeal pouch

Mulyipotent lymphoid stem cells invade epithelial rudiment to differentiate as T lymphocytes

Therefore- lymph Ophelia lymph organ

Epithelial component- ERCs(epithelial reticular cells)

52
Q

Describe the structural integrity of the thymus

A

Covered by a thin CT capsule

Trabeculae run within to divide tissue as lobules

Each lobule has a cortical cap over portions of highly convoluted but continuous inner medullary tissue

53
Q

Describe the parenchyma of the thymus

A

Cortex of parenchyma :
-mainly immature T lymphocytes (thymocytes ) & ERCs (epithelial reticular cells)

Medulla of parenchyma:
-mature T lymphocytes & ERCs

54
Q

Explain the significance of epithelial reticular cells (ERC’s)

A

Thymic epithelial reticular cells(ERC’s)- primary support cells in the cortex

Form a cytoreticulum-held together by Desmosomes

Blood vessels in cortex ensheathed by ERC’s

Sequester the developing T cells from blood borne antigens

55
Q

Where is the blood supply of the thymus?

A

Enter through trabeculae into cortex and medulla

Characterized by continuous capillaries

56
Q

What are the components of the blood thymus barrier?

A

A. Capillary endothelium

B. Capillary basal lamina

C. Perivasculaar connective tissue

D. Epitheliorecticular tissue

E. Epitheliorecticular cell

Blood thymus barrier found only in cortex

57
Q

Describe the cortex of the thymus

A

Cortex of tightly packed lymphocytes and support cells epithelial recticular cells (epithelial reticular cells)

Inner medulla- lymphocytes less concentrated

More of ERCs giving eosinophilic appearance

58
Q

Describe the medulla of the thymus

A

Blood vessels in medulla lose ERC covering

Lymphocyte differentiate and enlarge

Mature T cells migrate into medullary blood vessels and efferent lymphatics

  • ERC’s contract into spherical, degenerative masses- Hassall’s corpuscle
  • Hassal’s Corpuscle are found only in the thymic medulla and consist of rings of degenerating epithelial recticular cells
59
Q

What are lymph nodes?

A

Kidney or bean shaped organs of variable size

Distributed along the course of lymphatic vessels

Function- filters lymphatic fluid as it passes through them

Mounts immune response by recirculating of lymphocytes

60
Q

What are the parts of a lymph node?

A

Capsule- dense connective tissue
-pierced by afferent lymphatics

Outer cortex- collection of lymphocytes- prominent nodules
-abundance of B lymphocytes

Inner cortex/ para cortex - area between outer cortex and medulla

- collection of lymphocytes
- abundance of T lymphocytes
- no nodules

Medulla- cords and sinuses

Hilum- blood vessels and nerves (enter and leave): lymphatics exit

60
Q

What are the parts of a lymph node?

A

Capsule- dense connective tissue
-pierced by afferent lymphatics

Outer cortex- collection of lymphocytes- prominent nodules
-abundance of B lymphocytes

Inner cortex/ para cortex - area between outer cortex and medulla

- collection of lymphocytes
- abundance of T lymphocytes
- no nodules

Medulla- cords and sinuses

Hilum- blood vessels and nerves (enter and leave): lymphatics exit

61
Q

Outline the flow of lymph?

A

Afferent lymph vessels—> subscapular (cortical) sinus—> trabecular sinus—> medullary sinus —> efferent lymph vessel

62
Q

What are the features of the stroma of the lymph node?

A
  1. Reticular cells (modified fibroblasts)- cytoplasmic extensions cover reticular fibers (collagen type III )
  2. Framework for myeloid organs: bone marrow, lymph node & spleen
63
Q

Describe the outer cortex of the thymus

A

Area between capsule and medulla

Characterized by the presence of lymphatic nodules

Primary and secondary nodules

Mainly consisting of B lymphocytes

Presence of few T lymphocytes, macrophages, reticular cells and APCs

64
Q

Describe the para cortex /deep/inner cortex of the thymus

A
  • Area between outer cortex and medulla
  • primarily comprises T lymphocytes
  • Characterized by the presence of high endothelial venules
  • HEVs- allow for the transition of lymphocytes from the blood stream to lymph tissue within lymph node
  • Excess lymph fluid circulating within a lymph node (average 35%) is reabsorbed into these vessels
65
Q

Discuss the medulla of the thymus

A

Cords:
-branched cordlike extension of dense lymphoid tissue

-contain primarily B lymphocytes, plasma cells, reticular cells and macrophages

Sinuses:
- Dilated spaces separating medullary cords

  • Contain lymph, few wandering macrophages
  • Granulocytes maybe present when lymph node is draining an infected region

CPR 2 (32 decks)

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