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Immunology > Principles of Adaptive Immunity > Flashcards

Principles of Adaptive Immunity Flashcards

1
Q

Innate Immunity

A

Focus defense mechanisms onto the site of infection

  • Non specific
  • Non adaptive (no memory)
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2
Q

Adaptive Immunity

A

Focus defense mechanisms onto the pathogen itself

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3
Q

Specificity

A

Lymphocytes express antigen receptors that recognize specific features (antigens) of a microorganism = adaptive immune system can distinguish between different microorganisms

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4
Q

Immune Memory

A

Second encounter with the same pathogen will induce a more rapid and efficient adaptive immune response

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5
Q

Naive Lymphocytes

A

Have been exported from primary lymphoid tissues into blood and secondary lymphoid tissues

  • have not been activated in response to an infection
  • function: survey the body for infection
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6
Q

Effector lymphocytes

A

Activated lymphocytes that undergo proliferation and are specialized to perform a particular function
- effector function: how they eliminate pathogens from the body

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7
Q

Pathogen

A

Microbe that allows it to interfere with bodily functions and cause disease

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8
Q

Series of events that occur after pathogens adhere to epithelium

A

Skin wound allows pathogens to penetrate epithelium –> proinflammatory cyto/chemokines are released –> local infection, innate immunity –> DC take infection to lymph node and stimulate adaptive immunity –> effector cells and molecules of adaptive immunity travel to the infected tissue

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9
Q

B-lymphocytes (B cells)

A

B cell receptor is also referred to as an immunoglobulin (Ig)
- Soluble forms of BCRs referred to as antibodies

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10
Q

T-lymphocytes (T cells)

A

Surface expressed T cell receptor

- TCR is NEVER secreted

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11
Q

Structure of BCR and TCR

A

Variable region: antigen binding

Constant region: anchor the receptor to the cell membrane (associated with signal transduction proteins)

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12
Q

When the BCR is secreted as an _______, the constant region determines the effector function of the antibody

A

Antibody

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13
Q

What cell type is the bridge between adaptive and innate immunity?

A

Dendritic cells

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14
Q

Where do B cells and T cells develop?

A

Bone marrow; Thymus

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15
Q

What components of pathogens do antigen receptors recognize?

A
  • Protein, carbs, and lipids

- Risk of developing cells that recognize self-protein/carbs/lipids

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16
Q

Macrophages and neutrophils have ____ with broad specificity to recognize multiple microbes and distinguish between self and non self

A

TLR (toll like receptor)

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17
Q

_____ and _____ come together to form antigen-binding site

A

Heavy and light chains

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18
Q

Do B and T cells recognize the same form of the same antigen?

A

NO, recognize different forms of the same antigen due to their effector functions

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19
Q

BCR recognizes ____ of an antigen

A

The native form

20
Q

What part of the antigen do TCR recognize?

A

Peptides derived from the proteolytic degradation of the antigen

21
Q

Pathway of TCR recognition

A

Native protein antigen –> denatured protein –> peptide antigens derived from denatured protein –> TCR bind to peptide:MHC molecule complexes

22
Q

T cell effector function

A

To detect infected cells and provide activation signals to other leukocytes (controlling adaptive immune response)

23
Q

How do dentritic cells activate adaptive immunity?

A

DC are present in tissues, along with macrophages

  • when innate becomes overwhelmed, DC engulf pathogen and migrate to lymph nodes via afferent lymph vessels
  • OR, pathogens can be carried to lymph nodes and then entangled by DC
  • OR, pathogens in blood can be engulfed by DC in the spleen
24
Q

Role of APC in activating adaptive response

A

Naive T cells entering lymph node can survey the antigens displayed by DCs
- antigen specific T cells will be activated to proliferate and differentiate into effector T cells

25
Q

Effector T cells migrate to ____

A

Site of infection from the lymph nodes

26
Q

Effector function

A
  • activate macrophages to kill pathogens taken up by phagocytosis (helper T cells)
  • kill infected cells (cytotoxic T cells)
27
Q

What happens to the other portion of helper T cells (effector T cells)?

A

Remain in lymph node and provide activation signals to antigen specific B cells

28
Q

Function of bone marrow and thymus

A

Maintain a steady state production of B and T cells with varying receptors

29
Q

Dendritic cells

A
  • Antigen processing: potent in activating T cells, degrade phagocytized pathogen and display a piece on the surface by MHC
  • Antigen presentation
30
Q

Dendritic cells provide the ____ and the ____ _____ for adaptive response

A

Antigen; activation signal

31
Q

Major Histocompatibiliy Complex (MHC)

A

Complex of immune system genes that encode membrane proteins, which are involved in presenting peptides to T cells

32
Q

Do MHC proteins have broad or specific specificity?

A

Broad, can bind peptides derived from many different pathogens

33
Q

MHC class 1

A

Expressed on surface of most nucleated cells in the body

- recognized by cytotoxic T cells that express co receptor CD8

34
Q

MHC class 2

A

Expressed on surface of 3 leukocyte lineages:

  • DC, macrophages, B cells
  • recognized by helper T cells that express co receptor CD4
35
Q

Function of MHC class 1

A

Reports the “health status” of the cell
- proteins in the cell are degraded into short peptides after performing their function –> peptides are pumped into the ER and bound by newly synthesized MHC 1 proteins –> transported to cell surface

36
Q

Viral proteins and MHC 1

A

Viral proteins can also be degraded in the cytoplasm and transported to ER –> bind to MHC 1 –> MHC 1-viral peptide complexes will accumulate on surface of the cell for recognition by virus-specific CTL (cytotoxic T cells)

37
Q

Activation of CTLs

A

Activated in secondary lymphoid tissues by DC

  • proliferate/differentiate to effector CTL –> enter circulation and are recruited to site of viral infection
  • effector function: recognize/eliminate infected host cells
38
Q

Function of MHC class 2

A

Extracellular pathogens!

  • macrophage engulfs/degrades bacterium into peptides –> peptides bound by MHC 2 and transported to cell surface –> helper T cell recognizes complex and activates macrophage
  • effector helper T cells are recruited to site of infection and will activate effector function of other leukocytes responding to infection (macrophages and B cells)
39
Q

Effector helper T cell activation of macrophages

A 
Some pathogens (listeria) can resist being killed in macrophage lysosomes and persist in cytoplasm
- effector helper T cells activate macrophage production of powerful reactive oxygen species to kill intracellular bacteria
40
Q

B cell response to infection in secondary lymphoid tissues

A

Antigen binds to B cell receptor –> facilitates internalization of the antigen for processing and presentation by MHC 2 proteins

  • activation by effector helper T cells will induce B cell proliferation/differentiation to plasma cells
  • plasma cells synthesize and secrete original antigen receptor as antibody
41
Q

Effector helper T cell activation of B cells

A

Cell-surface immunoglobulin of B cell binds to bacteria –> cell engulfs and degrades them = peptides –> bacterial peptides bound by MHC 2 in endocytic vesicles –> bound peptides transported by MHC 2 to the cell surface –> helper T cell recognizes complex of peptide antigen with MHC 2 and activates B cell

42
Q

Do B cell receptors and antibodies recognize native protein antigens?

A

Yes, DC can release unprocessed antigens that are recognized by B cells in addition to processed/presented antigens recognized by T cells

43
Q

____ signals are required for lymphocyte activation

A

2; important mechanism of peripheral tolerance (tolerance to self protein)
Signal 1: recognition of antigen
Signal 2: delivered by another cell in form of cytokines and surface proteins

44
Q

Antigen-activated T cells require a second signal provided by ____

A

Dendritic cells

45
Q

Antigen-activated B cells require a second signal provided by ______

A

Effector helper T cells

46
Q

DC and effector T cells must become ____ before they can activate mature T cells

A

Licensed (must have taken up a pathogen)

47
Q

Once B cells are activated by antigens, they have ______ to collaborate with helper T cells or they become unresponsive

A

24 hours

Immunology (28 decks)

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