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Immunology- Unit 1 > Lecture 2 > Flashcards

Lecture 2 Flashcards

1
Q

All blood cells stem from what kind of cell?

A

CD34+ pluripotent stem cell

Breaks into myeloid progenitor or lymphoid progenitor

Blood cells migrate to primary lymphoid organs at 13th week of gestation

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2
Q

Where are T cells produced?

A

Thymus

- where proliferation, differentiation, and maturation completion occur

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3
Q

Where are B cells produced?

A

Bone marrow

- where proliferation, differentiation, and maturation completion occur

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4
Q

Where are antigen- specific receptors localized on T cells and B cells?

A

On surface of the cells

Activation is always antigen- specific

Structure of receptors varies from 1 cell to another
- receptors are identical on a single cell

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5
Q

What leads to naive lymphocyte death?

A

Die after 1 -3 months if they do not recognize antigen

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6
Q

Describe the anatomy of the thymus

A

Soft organ in the mediastinum of thoracic cavity

Lobular

Medulla = where T cells develop

Hassall’s Corpuscle

  • in the medulla
  • involved in generation of T regulatory cells

Larger in infamy/ puberty
- small in adults

Replaced by fat and connective tissue in the elderly

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7
Q

When are the majority of T cells produced?

A

Produced early in life

Production stopped by age 40
- mainly circulating memory cells

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8
Q

What is a naive T cell?

A

T cell that has not yet been exposed to an antigen

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9
Q

Describe the generation of naive T cells in the thymus

A
  1. T cells make contact with specialized epithelial cells, dendritic cells, and tissue- specific macrophages in thymus
  2. Contact produces cytokines which provide mechanisms for selection and differentiation of T cells
  3. Naive T cells are maintained in periphery without proliferating
    • tested by stromal cells
    • apoptosis induced in reactive cells

Develop from T cell progenitors

  • derived from pluripotent stem cells in liver
  • migrate through blood into thymus
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10
Q

Describe T cell receptors

A

Each T cell has receptors specific for only 1 antigen

Receptors are generated by gene rearrangement from multiple, inherited germline genes

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11
Q

Differentiate between T helper cells and cytotoxic T cells

A

T helper cells:

  • express CD4
  • provide help for B cell growth and differentiation

cytotoxic T cells:

  • express CD8
  • recognize and kill virus- infected cells
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12
Q

Describe the pathway of functionally mature T cells

A

Migrate to secondary lymphoid tissues to mediate protection

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13
Q

Describe anatomy of bone marrow

A

Soft, sponge-like tissue in center of most bones

Produces white blood cells, red blood cells, and platelets

At birth, all bone marrow is red

  • during puberty, red bone marrow converts to yellow marrow
  • in adults, half bone marrow is red and half is yellow
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14
Q

Describe the role of the bone marrow with respect to immune cells

A

All immune cells and all B cells are generated in the bone marrow

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15
Q

Describe the generation of naive B cells in bone marrow

A
  1. Differentiation of B cells occurs within the fetal liver and after birth in the bone marrow
  2. Development of B cells involves contact with stromal cells and cytokines

B cells which react with self-antigens are eliminated

Many different B cells are generated
- each have unique specificity for a particular antigen
- due to unique receptors

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16
Q

Describe the recirculation of lymphocytes

A
  1. Lymphocytes develop from bone marrow stem cells
  2. Lymphocytes mature in generative lymphoid organs (primary)
  3. Mature lymphocytes circulate through the blood and bring antigens via lymph to secondary lymphoid organs
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17
Q

Describe lymphocyte recirculation under healthy conditions

A

Cells come into lymph node and find no antigen

After 1 or 2 hours, enter lymph > exit back into circulation > cycle begins again

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18
Q

Antigens are captured from an ___ ___ and are transported into a ___. This is where what event takes place?

A

Infection site
Draining lymph node

This is where the immune response is initiated

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19
Q

Lymphocytes continuously circulate in all parts of the body except for in the ___?

A

Eye
Brain
Testicle

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20
Q

Define High Endothelium Venues

A

Specialized endothelium of post capillary venues through which the lymphocytes enter the secondary lymphoid organs

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21
Q

How are B and T cells different than neutrophils with respect to entering lymph nodes?

A

They enter at constituent levels and do not need inflammation/ inflammatory response to enter

They enter where antigen was delivered to lymph node

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22
Q

What do the cells of HEV express?

A

Express high levels of adhesion molecules
- serve as homing receptors for lymphocytes

They are higher than normal endothelial cells

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23
Q

How do lymphocytes enter into the tissue and what is this driven by?

A

Transmigrate via diapedesis into the tissue in response to chemokines

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24
Q

How do lymphocytes re-enter the circulation?

A

Via efferent lymph vessels that merge into the thoracic duct

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25
Q

Lymphocytes can be activated by ___ ___ in ___. If they are not activated, the lymphocytes are considered ___ and return to the ___ by ___ ___.

A

Foreign antigens; secondary lymphoid tissues

Naive; blood; lymphatic drainage

26
Q

Describe the activation of B cells starting at the entry of infectious agents/ environmental antigens into tissues

A
  1. Infectious agents/ environmental antigens enter tissues
  2. Collection of antigens from tissues via lymph
  3. Enter lymph node via afferent lymph vessel
  4. At the same time, antigen is drained and B cells are constantly circulating and looking for antigen.
  5. B cells are activated when they find the antigen and enter the lymph node.
  6. Activation of lymphocytes and initiation of adaptive immune response.
27
Q

Describe the activation of B cells starting with antigens/ microbes in the blood

A
  1. Collection of antigens via the blood
  2. Go to spleen (secondary lymphoid organ)
  3. When enter spleen, B cells create antibodies and move into tissue from where antigen was brought
  4. Migration of effector cells and blood delivery of antibodies to site of infection
28
Q

Describe the steps of B cell activation

A
  1. Naive B cells migrate into the secondary lymphoid tissues without help
    • look for and respond to soluble foreign antigens
  2. Antigen- activated B cells proliferate in germinal centers and mature into memory cells or into plasma cells
    • have limited numbers so need proliferation first
  3. After this turn into a lot of different antibodies
29
Q

Define Plasma Cell

A

Terminally differentiated B cells which produce and secrete large amounts of antibodies

Minimal cell maintenance
- very stressed so only lives 5 days and then undergoes apoptosis

30
Q

What do antigen- activated B cells primarily produce in the spleen?

A

Antibodies against microbial antigens in the blood

31
Q

Describe B and T cells in relation to spleen morphology

A

T cell and B cell zones make up the white pulp

T cells are located in periarteriolar lymphoid sheath (PALS)

B cells are located in lymphoid follicle with a germinal center

32
Q

Is there delivery of antigens by dendritic cells in the spleen? What compensates for this?

A

No delivery by DC

Resident dc’s grab antigens from blood and bring hem to presentation of B cells
- some antigens are presented to T cells

33
Q

How do secondary lymphoid organs act like a filtering system? Which organ is an example of this?

A

Take antigens from lymph nodes or the blood and retain them for some time (to activate immune cells)

34
Q

Describe the morphology of plasma cells

A

Have mitochondria, nucleus, RER, and Golgi

Rarely found in the peripheral blood but make up 0-3% of the bone marrow white cell count

35
Q

What is the function of plasma cells?

A

Secretion of antibodies

36
Q

Describe the activation of T cells starting at the entry of infectious agents/ environmental antigens into tissues

A
  1. Infectious agents/ environmental antigens are taken into tissues by dc
  2. DC’s are activated and digest antigens into peptides to present to T cells and are sent to secondary lymphoid organ
  3. Collection of antigens from tissues via lymph
  4. Enter lymph node via afferent lymph vessel
  5. Antigen is not drained but is taken into tissue by DC
  6. At the same time, native T cells are taken into the lymph node
37
Q

Describe the activation of T cells starting with antigens/ microbes in the blood

A
  1. Collection of antigens via the blood
  2. Go to spleen (secondary lymphoid organ)
  3. When enter spleen, have activation of lymphocytes and initiation of adaptive immune response
  4. Stimulates activation of effector T lymphocytes and creation of antibodies (B cells)
  5. Migration of effector cells and blood delivery of antibodies to site of infection
38
Q

Describe the steps of T cell activation

A
  1. Naive T cells migrate into secondary lymphoid organs (lymph nodes) in search of foreign antigens
    - enter from the blood and go to secondary lymphoid organ
    - exit if antigens are not present
  2. T cells which are activated by antigens differentiate into effector or memory T cells
  3. Some effector and memory T cells migrate back into the peripheral sites of infection via efferent lymphatics
  4. Some activated and differentiated T cells remain in the lymph nodes and help antigen- activated B cells to become an antibody factory
39
Q

Describe the morphology of the lymph nodes

A

B cell zone on periphery (follicle and germinal center)

T cell zone in the inside/ middle (in the medulla)

  • located here bec this is where also find DC
  • when antigens are not drained by T cells, they move to B cell zone

Afferent lymphatic vessel bring in antigens

Efferent lymphatic vessel take antigens/ stuff out
- could become afferent for a different LN

40
Q

Why is the lymph node considered a filtering device?

A

Has afferent and efferent functions

Cells are designed to store antigens

41
Q

How are cells directed in lymph nodes?

A

Chemokines send cells to either B zone or T zone

Do not have receptors by the messages are selective
- ex: T cell specific chemokine

42
Q

What is the mechanism behind how dendritic cells enter the lymph node?

A

Follows chemokine gradient produced by stomal cells

43
Q

Describe the pathway of naive T and B cells and dendritic cells in the lymph nodes

A
  1. Naive T and B cells enter the lymph node through an artery leaving the circulation by moving across the HEV
  2. B and T cells migrate to different zones of the lymph node directed by chemokines that are produced in these areas by stomal cells
  3. Dendritic cells pick up antigens from the sites of antigen entry and enter through afferent lymphatic vessels
  4. DC’s migrate to the T-cell rich areas of the LN
    • bypass the B zone
44
Q

Relate antigen presence to inactive/active lymph nodes

A

No antigens present in inactive lymph nodes

Active lymph nodes have antigens present

45
Q

Describe primary follicles

A

In absence of antigen stimulation, follicles are considered primary

Made of small naive B cells or recirculating memory B cells

Inactive lymph nodes

46
Q

Describe secondary follicles

A

With antigen stimulation, B cells proliferate and differentiate
- converts primary follicle into a secondary follicle or germinal center

Active lymph nodes

47
Q

Examples of professional antigen- presenting cells

A

Dendritic cells
Tissue macrophages
B cells

These cells can also be unprofessional but no other cells can be professional

48
Q

Define antigen- presenting cells

A

Cells that capture, process, and display antigens to T lymphocytes

Provide signals that stimulate the proliferation and differentiation of the lymphocytes

Involved in the presentation of the antigen and the activation of T cells

49
Q

Compare APC interaction with T cells and B cells

A

APC displays antigen to T cells

B cells do not need APC

50
Q

Describe role of dendritic cell as APC

A

Only DC’s are able to activate naive T cells in the lymph nodes

Naive cells are dormant and need to be “woken up”
- DC capacity surpasses B cells and macrophages

51
Q

Describe the role of tissue macrophages and B cells as APC

A

Can present antigens only for activated T cells but not naive T cells

52
Q

Relate dendritic cells and tissue macrophages as APCs to the relationship between innate and adaptive immunity

A

DC’s and tissue macrophages are cells of innate immunity.

Provide link between innate and adaptive immunity

53
Q

Describe classical dendritic cells function, location, and lineage

A

Take antigen and enter lymph node to stimulate T cells

Epidermis of skin
- develop directly from stem cells

Bone marrow> Hematopoietic stem cell > monocyte DC precursor > common DC precursor > pre-classical DC > classical DC

54
Q

Describe Plasmacytoid dendritic cell function and lineage

A

Never leave the tissue

Activate anti-viral responses

Epidermis of skin
- develop directly from stem cells

Bone marrow > Hematopoietic stem cell > monocyte DC precursor > common DC precursor > plasmacytoid DC > plasmacytoid DC

55
Q

Describe Inflammatory dendritic cell function and lineage

A

Allows us to restore pool of DCs located in all tissues

Bone marrow > monocytes

56
Q

Describe Langerhans cell function and lineage

A

Located in dermis, function not super known

Epidermis of skin
- develop directly from stem cells

Fetal hematopoietic organs > hematopoietic stem cell > embryonic tissue precursor > langerhans cell

57
Q

How do dendritic cells acquire antigens?

A

Phagocytosis
Receptor- mediated endocytosis
Pinocytosis

58
Q

Dendritic cells express receptors that recognize antigens made by ___?

A

Microbes

Do not express receptors that recognize antigens made by mammalian cells

59
Q

What do activated dendritic cells secrete?

A

Cytokines

60
Q

Compare Classical vs Plasmacytoid dendritic cells

A

C: reside in skin, mucosa, and organ parenchyma
- when activated by microbes, they migrate to lymph nodes where they display microbial protein antigens to T lymphocytes

P: early cellular responders to viral infection

  • recognize nucleic acids of intracellular viruses
  • produce soluble interferons
61
Q

IFN- alpha/ beta is related to plasmacytoid dendritic cells how?

A

Produced by plasmacytoid dendritic cells

Have potent antiviral activities

Immunology- Unit 1 (3 decks)

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