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IMM Exam 2 > Lymphoid Tissue > Flashcards

Lymphoid Tissue Flashcards

1
Q

Encapsulated lymphoid tissues

A

Thymus
Tonsils (can lack a capsule)
Lymph nodes
Spleen

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2
Q

Diffuse lymphoid tissue

A

MALT

  • Galt
  • Balt
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3
Q

Lymphoid cells

A

B cells
T cells
Macrophages

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4
Q

B cells

A
  • originate in bone marrow
  • mature in bone marrow
  • migrate to secondary structures
  • can become plasma cells
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5
Q

T cells

A
  • originate in bone marrow
  • mature in thymus
  • migrate to secondary structures
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6
Q

Macrophages

A

derived from monocytes

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7
Q

Where do you find IgG?

A

Many locations (75% of serum immunoglobulins)

  • produced in large amounts during immune responses
  • the only immunoglobulin to cross placental barrier (to protect newborn from infections)
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8
Q

Where do you find IgA

A

Nasal, bronchial, intestinal and prostatic secretions; also tears, colostrum, saliva and vaginal fluid

(5-10% Ig in serum)

  • secreted by plasma cells in lamina propia of epithelium if GI, respiratory and urinary passages
  • present in secretions in secretory form that is resistant to several enzymes; provides protection in secretions against microorganisms
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9
Q

Where do you find IgM?

A

Plasma membrane of B cells or in circulating form (10% Ig in serum)

  • IgM in the membrane, when bound to an antigen, causes differentiation of the B cell into an antibody-secreting plasma cell
  • Secreted IgM, when bound to antigen, activates the complement system
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10
Q

Where do you find IgE?

A

Surfaces of mast cells and basophils (5-10% Ig in serum)

  • Only small amounts in blood since it is attached to cells via its Fc region
  • They stimulate release substances (e.g. histamine), triggering an allergic reaction.
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11
Q

Where do you find IgD?

A

Plasma membrane of B cells or in circulating form (0.2% Ig in serum)

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12
Q

X-linked agammaglobulinemia

A

B lymphocytes do not develop, resulting in a scarcity of plasma cells and a lack of immunoglobulin production

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13
Q

CVID (common variable immunodeficiency)

A

Normal B cell population but do not make enough immunoglobulins

symptoms:
- recurrent respiratory infections
- autoimmune disorders (RA, thyroiditis, Addison disease)
- GI disorders (diarrhea and malabsorption of nutrients in GI tract)

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14
Q

Reticular cells

A
  • Form supporting framework of lymphoid organs (lymph nodes, spleen and bone marrow)
  • Synthesize reticular fibers
  • May be phagocytic
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15
Q

Nonencapsulated clusters of lymphoid cells or nodules

A

Diffuse lymphoid tissue

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16
Q

Peyer’s patches

A

Large aggregates of lymphoid nodules in the ileum, pushing into submucosa

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17
Q

Primary nodules

A
  • no germinal center

- composed of mostly RESTING B CELLS as well as plasma cells, dendritic cells, macrophages and reticular cells

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18
Q

Secondary nodules

A
  • formed in response to antigenic challenge
  • germinal center (developing B cells)
  • mantle/corona (darker periphery of displaced resting b cells, memory cells, plasma cells, DCs, macrophages and reticular cells)
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19
Q

Lymph node

A
  • Maintains/produces B cells and T cells
  • Possess memory cells (esp. T memory cells)
  • Primary location for filtration of lymph
  • Antigens delivered to lymph nodes by APCs are recognized by T cells, and an immune response is initiated

-contains: capsule, cortex/medulla, lymphoid nodules, hilum

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20
Q

primary location for filtration of lymph

A

lymph node

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21
Q

Vessels of lymph node

A
  • Convex surface of lymph node receives afferent lymphatic vessels
  • Concave surface (hilum) is where arterioles enter; venules and efferent lymphatic vessels exit
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22
Q

Antigens delivered to lymph nodes by APCs are recognized by _________, and an immune response is initiated

A

T cells

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23
Q

Lymph node cortex

A
  • Lymphoid nodules (mainly B cells)

- subcapsular and cortical sinuses (sinusoids)

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24
Q

Lymph node paracortex

A
  • Mainly T cells
  • T cells enter paracortex via “High-Endothelial Venules” (specialized post-capillary venules with a cuboidal epithelium)
  • known as “thymus-dependent area”
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25
Q

What is the “thymus-dependent area” in the lymph node?

A

paracortex

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26
Q

Lymph node medulla

A
  • Medullary sinuses (sinusoids) composed of reticular fibers/cells and macrophafes
  • Medullary cords composed of lymphocytes and plasma cells
27
Q

High-endothelial venule

A
  • specialized postcapillary venule in paracortex of the lymph node
  • simple cuboidal epithelium
  • 90% of lymphocytes leave bloodstream and enter lymph node here by diapedesis
28
Q

90% of lymphocytes leave the bloodstream and enter the lymph node at the __________ by ___________

A

High-endothelial venule, diapedesis

29
Q

Most venules in the body have a _______________, but the High-endothelial venule has ___________

A

simple squamous epithelium; simple cuboidal epithelium

30
Q

Why do lymph nodes swell?

A

When the body fights infection or injury, lymph nodes PRODUCE MORE CELLS and therefore often swell

Lymph nodes usually swell near the site of injury

31
Q

When the Virchow’s node is enlarged

A

suggestive of abdominal metastasis

32
Q

Thymus

A
  • Maintains T cells
  • Primary location for T cell maturation
    contains: capsule, cortex/medulla
33
Q

The thymus does not possess lymphoid nodules

A

true - the thymus just contains a capsule and cortex/medulla

34
Q

Cells in the cortex of thymus?

A

Epithelial reticular cells

Thymocytes

35
Q

Epithelial reticular cells

A

(TECs) In cortex of thymus

  • pale
  • form meshwork within which T cells are tightly packed
  • have long processes that contact other reticular cells and surround cortex, isolating it
  • synthesize THYMOSIN (transforms immature T cells –> immunocomputent T cells)
36
Q

What is thymosin?

A

Synthesized by epithelial reticular cells in the cortex of the thymus

-a serum thymic factor, thymopoietin for transforming immature T cells into immunocompetent T cells

37
Q

Thymocytes

A

In cortex of thymus

  • respond to cytokines (released by TECs) and become T cells
  • migrate from cortex toward medulla as they mature (many die along the way and are phagocytosed)
  • surviving T cells are naive, leave thymys and travel in blood to secondary lymphoid organs
38
Q

What cells leave the thymus?

A

surviving T cells are naive; they leave the thymus and travel in blood to secondary lymphoid organs

39
Q

Blood-thymus barrier structure

A

in cortex of thymus

  1. capillary endothelium and basal lamina
  2. perivascular connective tissue w macrophages
  3. thymic epithelial reticular cells and basal lamina
40
Q

What creates an immunologically protected region, ensuring that antigens escaping the bloodstream do NOT reach developing T cells in the cortex?

A

the blood-thymus barrier

41
Q

Cells in Medulla of Thymus

A

Loosely packed Mature T cells and epithelial reticular cells

the loosely packed cells is why the medulla is lighter staining than the cortex

42
Q

Where are Hassall corpuscles?

A

In the Medulla of Thymus

43
Q

Hassall corpuscles

A

(Thymic corpuscles)

  • Whorl-like accretions of epithelial reticular cells
  • keratinized
  • increase in # w age
  • unknown function
44
Q

Mature T cells exit the thymus via

A

venules and efferent lymphatic vessels from the thymic medulla

45
Q

DiGeorge syndrome

A

aka Congenital thymic aplasia

-abnormal cell-mediated immunity but normal humoral immunity

CATCH 22: Cardiac defects, Abnormal facies, Thymic hypoplasia, Cleft palate, Hypocalcemia, microdeletion of chromosome 22

46
Q

In the thymus, positive selection occurs in the

A

cortex

47
Q

In the thymus, negative selection occurs in the

A

medulla

48
Q

Filters blood

A

spleen

49
Q

Spleen

A
  • Maintains/produces B cells and T cells
  • Filters blood
  • Stores RBCs; phagocytoses damaged/aged RBCs
  • Prenatal, extramedullary hematopoiesis

Contains: capsule, lymphoid nodules, hilum

50
Q

How is the spleen different from both the thymus and lymph nodes?

A

it lacks a cortex and medulla

51
Q

The spleen lacks a cortex and medulla

A

true

52
Q

Does the spleen have afferent lymphatic vessels?

A

No. but the lymph nodes have afferent lymphatic vesseles

53
Q

Spleen White pulp

A

Lymphoid nodules = B cells

Periarterial lymphatic sheath (PALS) = T cells

54
Q

Spleen Red pulp

A

Interconnected network of sinusoids and splenic cords

sinusoids lined by stave cells

cords (of billroth) has plasma cells, reticular cells, blood cells and macrophages

55
Q

Spleen White pulp and Red pulp are separated by a

A

marginal zone

56
Q

The spleen is very vascular

A

true

57
Q

Organization/flow of vasculature in spleen

A

Splenic artery –> trabecular artery –>
central artery –>
penicillar artery –>
either (1) splenic sinusoiuds or (2) splenic cords

58
Q

Central artery is white or red pulp?

A

White pulp; covered by Periarterial lymphatic sheath (PALS), T cells

59
Q

Penicillar artery and its branches are white or red pulp?

A

red pulp

60
Q

The splenic artery enters the

A

hilum

61
Q

Splenic sinusoids are _______ circulation

A

closed

62
Q

Splenic cords are __________ circulation

A

open

63
Q

Marginal zone of spleen

A
  • between red and white pulp
  • first site where blood contacts pleen parenchyma
  • richly supplied by macrophages and APCs
  • circulating T cells and B cells are sorted here
64
Q

Tonsils

A
  • Maintain/produce B cells
  • Combat antigens entering via nasal/oral epithelia

Contains: capsule, lymphoid nodules

IMM Exam 2 (15 decks)

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