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Histology Final > Immune System > Flashcards

Immune System Flashcards

1
Q

immune System consists of:

A
  • cells: lymphocytes, antigen-presenting cells
  • lymphatic tissue: diffuse and nodular
  • lymphatic Organs: lmyph nodes, Spleen, Thymus
  • lymphatic vessels
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2
Q

Main functions of immune system

A
  • production of immune cells
  • Monitoring Body tissues
  • reaction to harmful Antigens
  • storage of blood and lymph
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3
Q

Antigen (Ag)

A
  • target for specific immune Response

- soluble substance or infectious organism

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4
Q

Cellular (cell-mediated) immunity

A
  • mediated by T lmyphocytes
  • attack and destroy virus-infected host cells
  • no antibodies released
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5
Q

Humoral (antibody-mediated) immunity

A
  • antibodies act directly on invading Agent

- antibodies produced by Plasma cells derived from B lymphocytes

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6
Q

Functional classification of lmyphocytes

A
  • B cells
  • T cells
  • NK cells
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7
Q

Morphological classification of lymphocytes

A

small
medium
large

in circulating blood: majority are small

in tissues and Organs: medium and large

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8
Q

T cells

A
  • differentiate in Thymus
  • 60-80% of circulating lymphocytes
subtypes:
Helper T
Cytotoxic T
Regulatory T
Gamma/Delta T
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9
Q

Helper T cells

A
  • secrete cytokines
  • interact with cytotoxic T, NK and macrophages in cellular Response
  • interact with B cells for initiating humoral response
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10
Q

Cytotoxic T cells

A
  • kill target cells
  • release:
    >perforins: create channels in cells Plasma membrane
    >granzymes: into target cells, activate apoptosis
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11
Q

Regulatory T cells

A
  • can supress an immune Response to Antigen
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12
Q

Gamma /Delta T cells

A
  • develop in Thymus
  • migrate to epithelial tissues (intraepithelial lymphocytes)
  • first line of defense against invadors
  • kill cells similar to CT cells
  • do not recirculate!
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13
Q

B cells

A

20-30%

- differentiate into Plasma cells

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14
Q

Plasma cells

A
  • large eccentric nucleus
  • synthesize and secrete anitbodies –> immunoglobins
  • immunoglobins M, A, D, E, G
  • antibody binds to Antigen: antibody-Antigen complex
  • eliminated by phagocytosis
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15
Q

Natural Killer (NK) cells

A

5-10%

  • recognize transformed cells (Virus or Tumor)
  • similar mechanism as CT cells
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16
Q

Antigen-presenting cells

A
  • lymphocytes can only recognize Antigens broken down and presented by APCs
  • Antigen –> 8 to 10 aa Peptides on APC cell Surface
  • most APCs belong to MPS
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17
Q

Mononuclear phagocytotic system

A
  • derived from monocytes

macrophages in CT, lungs, Spleen
Kupffer cell, microglia, M cells
Langerhans cells, Dendritic cells

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18
Q

Primary lymphatic organs

A

Bursa-equivalent Organs (for B cells)

  • bone marrow
  • gut-associated lymphatic tissue (GALT)

Thymus (for T cells)

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19
Q

Secondary lymphatic organs

A

lymphatic nodules
lymph node
spleen

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20
Q

Primary lymphatic Organs - what they do

A
  • initial education Centers
  • cells differentiate into immunicompetent cells
  • –> can differentaite “self” vs “non-self”
  • differentation is antigen-Independent
  • lymphocytes then enter blood to populate secondary organs
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21
Q

Secondary lymphatic Organs - what they do

A
  • secondary education Centers
  • immunocompetend lymphocytes differentiate into:
    >immune effector cells
    >Memory cells
  • These cells undergo antigen-dependent activation
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22
Q

Primary immune respinse

A
  • body’s first Encounter with an Antigen

- characterized by lag period of several days before Antigen is detected

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23
Q

Secondary immune response

A
  • more rapid and intense

- presence of Memory lymphocytes that are programmed to respond

24
Q

Bone marrow

A

YELLOW BONE MARROW:

  • in adults
  • consists of fat cells
  • occupies diaphysis of Long bones

RED BONE MARROW:

  • in adults: in flat bones and epiphyses of Long bones
  • in new Born: all bone marrow is red

in extreme blood loss: yellow marrow can revert to red marrow

25
Q

Red bone marrow

A

stroma: reticular cells and fibers with fat cells, fibrophages, macrophages…

parenchyma:
- blood cells in different stages arranged as Cords
- erythrocytes nest: near sinusoids
- granulocytes and lymphocytes: nest farther away from sinusoids
- Megakaryocytes: adjacent to sinusoidal wall

26
Q

Gut-associated lymphatic tissue

A

lymphatic nodules of the distal gut

  • submucosa of Ileum (Peyer’s Patches)
  • submucosa of appendix
27
Q

Thymus main functions

A

T-cell initial education

Population of secondary lymphatic organs

28
Q

Organization of Young thymus

A

dense irregular CT capsule

trabeculae divide into irregularly shaped lobes
Stroma: Epithelioreticular cells (ERCs)
Parenchyma: T cells /thymocytes

29
Q

Lobe of thymus

A

Cortex: a lot of lmyphocytes
Medulla: fewer lympocytes

30
Q

Developmental Sources of thymus

A

Stroma: endoderm (Invagination of Epithelium f 3rd pahyngeal pouch)

Capsule and trabeculae: mesenchyme

31
Q

Epithelioreticular cells (ERC)

A

Functions:

  • Framework for developing T cells
  • blood-thymus barrier
  • substances for education of cells
  • form thymic corpuscle
32
Q

Bloor-Thymus barrier

A

Endothelium of capillary wall
Perivascular connective tissue
Epithelioreticular cell layer

33
Q

T cell “initial education”

A

Enter MEDULLA via postcapillary venules

into CORTEX for positive selection
—> Cells that recognize self/non-self pass

into MEDULLA for negative selection
—> Cells that recognize SELF antigents are eliminated

34
Q

Thymic (Hassall’s) corpuscle

A
  • In Medulla of older Thymus
  • produce Interleukins –> influence Differentiation of T cells
  • concentrically arranged ERCs
  • in Center: keratinization or calcification
35
Q

Thymic involution

A
  • at puberty
  • T cells leave the Thymus to populate secondary lymphatic Organs
  • Thymus Skinks and fills with Hassall’s corpuscle and fat cells
36
Q

MALT

A

mucosa-associated lymphatic Organs

accumulations of lymphatic tissue without capsule

GALT is part of MALT

consists of intraepithelial lypmocytes (Gamma /Delta T)

37
Q

Diffuse lymphatic tissue

A

diffuse Aggregation of lymphocytes in LAMINA PROPRIA of:

  • GI
  • Respiratory
  • Urogenital
38
Q

Lymphatic nodules

A
  • oval Aggregation of lymphocytes in
    LAMINA PROPRIA or SUBMUCOSA

composed of T and B cells, antogen presenting cells

Primary vs secondary nodules

39
Q

Primary nodules

A
  • lmyphocytes are not activated

- no germinal centers

40
Q

Secondary nodules

A
  • germinal Centers
  • when B cells are presented with Antigen, reveice T cell help
  • B-cells –> lmyphoblasts –> Plasma cells and Memory cells (this happens in germinal Centers)
41
Q

Tonsils (MALT of Pharynx)

A

form waldeyer’s tonsillar ring

pharyngeal tonsils
Tubal tonsils (around Openings of Eustachian tubes)
—> These two have Respiratory Epithelium

Palatine tonsils
Lingual tonsils
—> These two have stratified squamous epithelium

42
Q

Structure of the tonsils

A
  • Epithelium Dips into Underlying CT to form crypts

- wall of crypts contains intraepithelial lmyphocytes, diffuse lymphatic tissue and lymphatic nodules

43
Q

Lymph nodes

A
  • conctentrated in Axilla, groin, mesenteries
  • encapsulated
  • Filtration and contact with Antigen
  • Environment for secondary education
44
Q

Lymph node structure

A

capusle: dense CT
Stroma: reticular CT
Parenchyma: immune cells

Cortex (B cells in Primary and secondary nodules)
Paracortex (T cells)
Medulla (B cells and medullary Cords and sinuses)

look at Picture!!!!!!

45
Q

Lmyphatic circulation of lymph node

A
  1. afferent lmyphatic vessels
  2. subcapsular Sinus
  3. trabecular Sinus
  4. medullary Sinus
  5. efferent lymphatic vessels

in sinuses: lmyph with macrophages and reticular cells

46
Q

Blood circulation in lmyph node

A 
artery in Hilum
arterioles in paracortex
capillary beds in Cortex
high endothelial postcapillary venules in paracortex
hilar vein
47
Q

High endothelial postcapillary venules

A
  • cuboidal endothelial cells
  • important in circulating and concentrating lymph
  • site of Exit of lymphocytes (90%)
48
Q

Spleen organization

A
  • capsule (dense CT and myocytes)

stroma: reticular CT
Parenchyma: blood cells

White Pulp vs red Pulp

look at Picture!!!!!!

49
Q

Main functions of spleen

A

immune functions:

  • filters and Monitors blood
  • Environment for secondary education

Hematopoietic function:

  • Formation of blood cells in fetal life
  • removal of RBCs and platelets
  • Retrieval of ion

Storage of blood

50
Q

Splenic circulation

A

open circulation in humans:

  1. Splenic artery
  2. Trabevular arteries
  3. Penicillar arterioles
  4. Red Pulp
  5. Spleic Cords
  6. Splenic sinuses
  7. Pulp venules
  8. Trabecular vein
  9. Splenic vein
closed circulation in animals
…
Penicillar arterioles
capillaries
splenic sinuses
...
51
Q

White Pulp of spleen

A

lmyphatic Aggregation around central arteries

  • periarterial lmyphoid sheaths (PALS, mostly T cells)
  • lmyph nodules (mostly B cells)
52
Q

Splenic follicle

A

Periarterial Zone: around central artery, T cells

Germinal Center (B cells)

Mantle Zone (around germinal Center) T and B cells

Marginal Zone (around follicle) T and B cells

53
Q

Red Pulp of spleen

A

splenic Cords

splenic sinuses

54
Q

Splenic cords

A

Contain blood cells: RBCs , neutrophils, pletelets, macrophages

Reticular Framework supports the Cords

Cords are between sinusoids

55
Q

Splenic sinuses

A

Endothelial cells
Discontinuous b.n.
Reticular fibers around sinuses

Histology Final (18 decks)

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