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D1 Fall - Histology > The Immune/Lymphoid System > Flashcards

The Immune/Lymphoid System Flashcards

1
Q

What are the functions of the protective surface inmmune system mechanism?

A
  • first line of defense in skin and mucous membranes
  • protected by a variety of antibacterial substances including defensins and lysozymes (in tears and saliva)
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2
Q

What are the three main lines of defense for humans?

A
  1. protective surface mechanisms
  2. innate immune system
  3. adaptive immune system
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3
Q

What are the functions of the innate immune system?

A
  • rapid reaction to a pathogen
  • same magnitude of reaction with each encounter (no learning)
  • cells, proteins, peptides that circulate in the blood
  • many of the same cells and signaling molecules used in innate are vital in the adaptive as well
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4
Q

What are the characteristics of acute inflammation?

A
  • vascular changes including dilation, enhanced permeability of capillaries, and increased blood flow
  • production of fibrin-rich inflammatory exudate
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5
Q

What are the functions of the adaptive immune system?

A
  • ability to learn so that the subsequent response elicits a greater, more specific, faster response
  • uses T and B lymphocytes
  • requires antigen-representing cells
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6
Q

What are the actions of the neutrophil, eosinophil, and macrophage?

A

Phagocytosis and killing of pathogenic organisms
Secretion of cytokines and extracellular antimicrobial
molecules, including neutrophil extracellular traps
(NETs) and pattern recognition molecules (PRMs)

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7
Q

What are the actions of the complement and chemokines?

A

Opsonises organisms to facilitate phagocytosis
Chemoattractant for various cells
Membrane attack complex (MAC) kills cells by
puncturing plasma membrane

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8
Q

What are the actions of the natural killer (NK) cells?

A

Recognize and kill virus-infected and cancerous cells

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9
Q

What are the dense lymphoid tissues?

A
  • organized into discreet structures or organs (lymph nodes, spleen, thymus, tonsil)
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10
Q

What are the diffuse lymphoid tissues?

A

—located throughout body, associated with mucous membranes

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11
Q

What is primary lymphoid tissue?

A

— lymphoid tissue where b- & t-cells acquire surface receptors
— bone marrow for b cells and thymus for t cells

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12
Q

What is the secondary lymphoid tissue?

A

Mature b- & t-cells secondarily migrate to all other lymphoid tissue

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13
Q

What are malignant tumors of the immune system called when they involve a solid organ?

A

lymphomas

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14
Q

What are malignant tumors of the immune system called when they involve blood?

A

leukemias

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15
Q

What do lymphatic vessels allow for?

A
  • route which allows cells and large molecules in ECM to re-enter the bloodstream
  • assist circulation of lymphocytes
  • concentrate antigens for elimination within lymph nodes
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16
Q

What activates a lymphocyte?

A

antigen binds to their surface receptor

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17
Q

What cell constantly patrols the body, circulates in blood,
lymph and extracellular fluid, and pauses in organized
lymphoid tissue?

A

lymphocytes

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18
Q

What does the binding of B cell receptors depend on?

A

shape and electrical charge

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19
Q

What does binding to T cell receptors require?

A

shape, electrical charge, and must bind to the major histocompatibility complex (MHC)

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20
Q

What are the roles of T-lymphocytes?

A
  • T helper cells (TH cells) - ‘help’ other cells to perform their effector functions by secreting a variety of mediators
  • Cytotoxic T cells (TC cells) - kill virus-infected and some cancer cells. They require interaction with TH cells to become activated and proliferate to form clones
  • Regulatory T cells (TREG) - suppress immune responsiveness to self-antigens (autoimmunity) and switch off the response when antigen is removed
  • Memory T cells - develop from activated T cells to provide a ‘rapid reaction force’ for a subsequent encounter with the same antigen
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21
Q

Which T cell s ‘help’ other cells to perform their effector functions by secreting a variety of mediators? TH cells thus provide ‘help’ to B cells, cytotoxic T cells and macrophages.

A

T helper cell

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22
Q

What T cells s are able to kill virus-infected and
some cancer cells and require interaction with TH cells to become activated and
proliferate to form clones?

A

Cytotoxic T cell

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23
Q

What T cell suppresses immune responsiveness to self-antigens (autoimmunity) and switch off the response when antigen is removed?

A

Regulatory T cell (TREG)

24
Q

What T cell is developed from activated T cells to provide a ‘rapid reaction force’ for a subsequent encounter with the same antigen and is the basis of persisting immunity?

A

Memory T cell

25
Q

Where do plasma cells develop and what do they do?

A
  • mature from B cells in the bone marrow
  • synthesize large amounts of antibodies (IgG, IgA, IgD, IgE, IgM)
26
Q

What are lymph nodes and how are they arranged?

A
  • encapsulated aggregates of lymphocytes & lymphoid tissue, distributed throughout the body
  • Arranged in chains or clusters along vessels of lymphatic origin (submandibular, cervical, axillary, femoral, popliteal)
27
Q

What are the four functions of lymph nodes?

A
  • Non-specific filtering of particulate matter & microbes from lymph
  • Interaction of circulating lymphocytes with Ag in lymph
  • Aggregation, activation, & proliferation of B-cells with subsequent Ab production
  • Aggregation & proliferation of T-cells & induction of cytotoxic immunity
28
Q

What are immune accessory cells?

A

antigen presenting cells (macrophages, b and t cells; originate in bone marrow)

29
Q

What are two types of immune accessory cells/macrophages?

A

– follicular dendritic cells - macrophages at periphery of germinal centers; Ag-presenting cells
– Tingible body macrophages - 1’ found in germinal centers; possess numerous phagocytic vesicles

30
Q

What are stromal cells in the lymph nodes?

A

fibroblasts and reticular cells

31
Q

What are the three cell types in the lymph nodes?

A

lymphoid cell
immune accessory cell
stromal cell

32
Q

What is the morphology of the lymph node?

A
  • Outer, fibrous capsule of dense, irregular connective tissue
  • dense, outer, cellular cortex (B and T-cells, & plasma cells) & less cellular inner medulla
  • Extensions of cortical tissue into medulla called medullary cords
  • Separated by medullary sinuses
  • Interspersed throughout cortex & medulla are very thin, collagenous trabeculae
  • Blood vessels enter & leave lymph nodes at hilus
33
Q

What type of follicle are densely packed, highly cellular, and located within the cortex of the lymph node?

A

primary follicle

34
Q

What type of follile is paler and contains less dense germinal centers?

A

secondary follicle

35
Q

Which type of follicle is responding to anitgens?

A

secondary follicle

36
Q

What does proliferation of lymphocytes via clonal expansion and other means do to lymph nodes?

A

enlargement and “swollen glands”

37
Q

What is the darker staining rim surrounding a germal center called?

A

mantleor marginal zone

38
Q

What is the space beneath the capsule where numerous afferent lymph vessels drain into?

A

cortical or subcapsular sinus

39
Q

What is the nature of the endothelium in the lymph node for lymphatic drainage?

A

endothelium on side adjacent to capsule - continous (prevents leakage)
endothelium on side adjacent to parenchyma - discontinous

40
Q

Are lymphatic sinuses open spaces like blood sinuses?

A

NO - filled with reticular fibers and macrophage processes

41
Q

What is the process where B and T cells leave the bloodstream and enter the node faciliated by complementary adhesion molecules?

A

diapedesis

42
Q

Where do B and T cells leave the bloodstream?

A

specialized post-capillary venules (high endothelial venules)
- lined by cuboidal to columnar endothelium (at the paracortical zone)

43
Q

What are the sinuses in the outer cortex of the lymph node?

A

cortical sinuses, trabecular sinuses, or peritrabecular sinuses

44
Q

What is the path of lymphatic drainage?

A
  • outer cortex sinus
  • medullary sinus
  • lymph drains from hilus of node via a single efferent lymph vessel
  • returns to blood stream via thoracic duct or right lymphatic duct
45
Q

What is the clinical relevace of lymphatic drainage to regional lymph nodes?

A

important in metastasis of tumor cells

46
Q

What are the functions of the thymus?

A
  • Production of mature, immunocompetent Th & Tc cells
  • Clonal proliferation of Tc cells
  • Clonal deletion of self-Ab’s
  • Secretion of hormones regulating t-cell development & maturation
47
Q

As t-cells mature in the thymus they express?

A
  • Ag specific t-cell receptors
  • CD (cluster of differentiation) surface markers
  • Class I & II HLA (human leukocyte Ag) surface markers
48
Q

What does the thymus have that is unique?

A

hassall’s corpuscles
- eosinophilic lamellated structures within both the medulla and cortex of the thymus
- either degenerated reticular or epithelium nurse cells

49
Q

What do nurse cells in the thymus secrete?

A

various hormones (thymotaxin, thymosin, & thymopoietin) to attract, regulate & promote t-cell proliferation & differentiation into Tc, Ts & Th cell

50
Q

What is the difference between lymph nodes and the thymus?

A
  • thymus is less cellular
  • thymus central medulla contains mostly b-cells, plasma cells, and macrophages
  • thymus lacks secondary follicles
51
Q

What is the structure of the thymus?

A

-highly cellular coretex (t-cells and macrophages)
- secondary follicles absent
- thin capsule of dense, irregular ct
- slender interlobular septa or trabeculae

52
Q

What is in the outer cortex of the thymus?

A

– Immature T-Lymphocytes
– Epithelial Cells (Nurse Cells); secrete thymic hormones
– Some Macrophages

53
Q

What is in the inner medulla of the thymus?

A

– Epithelia Cells
– Mature T-Lymphocytes
– Thymic Corpuscles (Hassall Corpuscles); Circular aggregations of aged, degenerated Nurse Cells

54
Q

Which organ degnerates at puberty and is vestigial in adults?

A

thymus

55
Q

What process allows for the thymus to degenerate?

A
  • fatty infiltraiton and lymphatic depletion (thymic involution)
  • no afferent lymph vessels to thymus because continous epithelium isolates it
  • blood-thymus barrier forms an antigenic barrer that isolates thymus from immune system

D1 Fall - Histology (20 decks)

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