Adaptive Immune System Flashcards

1
Q

What does “adaptive” or “specific” immunity mean?

A

adaptive immunity is immunity that is acquired over time after being exposed to a pathogen. It is a response that is adapted to target a specific pathogen.

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2
Q

Why does it take a while to develop the first time an individual is exposed to a pathogen?

A

it takes longer to develop because the body has not been exposed to the pathogen before.
- after the first exposure, the body develops memory so the next time it is exposed to the pathogen, it can give a faster and larger response that is specific to the pathogen.

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3
Q

What happens during the second exposure to a pathogen?

A

by the second exposure to a pathogen, the body already has memory of the pathogen.
- as a result, there is a faster and specific response in the second exposure to a pathogen.

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4
Q

What is an antigen?

A

a molecule unique to specific pathogens that the body recognizes and foreign.
- they stimulate the adaptive immune response.

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5
Q

What is an epitope?

A

small recognition sites on the surface of antigens.
- they are recognized by antibodies and B and T cell receptors.

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6
Q

Why are they important to the adaptive immune system?

A

antigens are important as they stimulate the adaptive immune system and create different responses as antibodies recognize and bind to their epitopes.

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7
Q

What are antibodies?

A

produced by plasma cells and help in the defense against pathogens.
- they bind to and recognize specific epitopes on antigens.

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8
Q

What are the 5 major classes of antibodies?

A

1) IgG
2) IgM
3) IgA
4) IgD
5) IgE

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9
Q

What are the structures of IgG, IgD, and IgE?

A

have two antigen binding sites but they each have different heavy chains (Y shape).

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10
Q

What is the function and abundance of IgG?

A

1) it can cross the placental barrier and provides natural passive immunity to the fetus.
2) also functions in agglutination, activation of complement, neutralization, opsonization, and cell-mediated cytotoxicity.
- relative abundance: 80% (most abundant).

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11
Q

What is the function and abundance of IgM?

A

1) its monomer form works as a B cell receptor.
2) also functions in agglutination, complement activation, and neutralization.
- relative abundance: 6%

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12
Q

What is the function and abundance of IgA?

A

1) it gets secreted into mucous membranes, the GI tract, and breast milk. Like IgG, it contributes to natural passive immunity from the mother to the baby.
2) it traps pathogens in mucus to be eliminated later. It also functions in neutralization.
- relative abundance: 13% (second most common antibody).

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13
Q

What is the function and abundance of IgD?

A

functions as an B cell receptor (antigen-binding receptor).
- relative abundance: <1%

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14
Q

What is the function and abundance of IgE?

A

activates basophils and mast cells to fight against allergens and parasites (pro-inflammatory).
- relative abundance: <1% (least abundant)

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15
Q

What does MHC stand for?

A

major histocompatibility complex

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16
Q

Why is MHC important in adaptive immunity?

A

they are molecules on the surface of healthy cells of the body.
- this helps identify themselves as normal cells to natural killer cells.
- MHC molecules help natural killer cells differentiate normal cells from infected cells.
- they also play a role in the presenting of foreign antigens.
- there are two classes, MHC I and MHC II in adaptive immunity.

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17
Q

What are APCs? What is their role in adaptive immunity?

A

antigen-presenting cells are the macrophages, dendritic cells, and B cells. These cells present antigens on their surface in order to activate T cells.

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18
Q

What is humoral immunity?

A

involves the production of antibodies to fight pathogens outside the cell

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19
Q

What is cellular immunity?

A

uses T cells to target and eliminate pathogens inside the cell

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20
Q

What are the primary components of the lymphatic system?

A

red bone marrow and thymus

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21
Q

What are the secondary components of the lymphatic system?

A

lymph nodes, spleen, tonsils, MALT

22
Q

What is the role of red bone marrow?

A

the location where elements of the blood are produced and differentiated
- B and T cells develop here.

23
Q

What is the role of the thymus?

A

immature T cells migrate here from the bone marrow
- it is the location where T cells mature.

24
Q

What is the role of the lymph nodes?

A

function in draining fluid and filtering out antigens from the lymph.
- the immune cells (macrophages and dendritic cells) present the captured antigens to the B and T cells to begin an immune response.

25
Q

What is the role of the spleen?

A

it filters antigens in the blood.
- B cells and T cells in the spleen are activated by antigen presenting cells that travel to the spleen through the bloodstream.
- B cells respond by producing antibodies.

26
Q

What is the role of the tonsils?

A

prevents pathogens from entering the respiratory tract and the digestive tract.
- it contains T cells to kill pathogens and B cells to produce antibodies that fight against pathogens.

27
Q

What is the role of MALT?

A

it begins an immune response against specific pathogens found on the mucosal surfaces.
- it produces IgA and secretes it in mucosal surfaces.

28
Q

How does positive selection on lymphocytes work?

A

positive selection works by checking whether a T cell can recognize cells with MHC molecules on their surface.
- If they do not react strongly to autoantigens, then they can circulate to other parts of the body.
- If they react strongly, they will undergo apoptosis.

29
Q

How does negative selection on lymphocytes work?

A

negative selection is done to check whether a lymphocyte reacts strongly to self-antigens.
- if they do react strongly, they are killed.

30
Q

Why is the positive-negative selection of lymphocytes important?

A

both positive and negative selection are necessary to prevent the formation of lymphocytes that attack normal cells of the body and minimize the risk of autoimmunity.

31
Q

What are the classes of T cells?

A

The three classes of T cells are helper T cells, regulatory T cells, and cytotoxic T cells

32
Q

How are T cells differentiated?

A

they are differentiated based on what surface molecules they express, their functions, and how they are activated.

33
Q

What is the function of Helper T Cells?

A

assist in activating and directing functions of both cellular and humoral immunity
- it helps activate macrophages and NK cells.

34
Q

What is the function of Regulatory T cells?

A

prevent immune responses that could be damaging to the body
- they play a role in the prevention of autoimmune responses and in peripheral tolerance

35
Q

What is the function of Cytotoxic T cells?

A

recognize, target, and destroy infected cells and the pathogens inside them

36
Q

What is the process of activation?

A

occurs when receptors on lymphocytes recognize epitopes on an antigen

37
Q

What is the process of clonal expansion/proliferation?

A

when the lymphocyte goes through mitosis repeatedly to produce many copies of itself
- it does this in order to fight and defeat pathogens.

38
Q

What is process of differentiation?

A

occurs when a lymphocyte becomes different subtypes of cells with specific functions.
- for example, helper T cells can differentiate into helper T I cells, helper T II cells, and memory helper T cells.

39
Q

What is the mechanism of superantigens?

A

superantigens are toxins produced by pathogens that trigger unregulated and excessive T cell activation.
1) superantigen locks an epitope and a T cell together and causes the T cell to become overactive.
2) this causes the production and overabundance of cytokines.

40
Q

How are B cells produced?

A

produced in the bone marrow from multipotent hematopoietic stem cells.
- lymphoblasts that will become B cells mature in the bone marrow.

41
Q

What is positive selection of B cells?

A

involves testing whether B cells have normal and functional receptors

42
Q

What is negative selection of B cells?

A

involves destroying B cells that react to self-antigens.
- self-reacting B cells are eliminated by apoptosis.
- if B cells pass selection, they travel to the spleen to complete their maturation and wait until they are activated.

43
Q

What is T dependent B cell activation?

A

T-dependent activation is more complex than T-independent. B cells cannot be activated solely by recognizing an epitope.
1) A helper T cell needs to recognize the antigen and release cytokines.
2) The cytokines then activate the B cell. The B cell responds by undergoing clonal proliferation and differentiation.
3) This leads to a stronger immune response and memory can be developed.

44
Q

What is T independent B cell activation?

A

T-independent activation is the activation of B cells without needing the aid of a helper T cell.
1) A B cell recognizes an epitope and becomes activated.
2) The B cell responds by undergoing clonal proliferation and differentiation.
3) The response is short lived compared to T-dependent activation. It also does not produce memory B cells or result in a secondary response.

45
Q

What is the primary response to T cell-dependent activation?

A

The primary response to T cell dependent activation ends in the production of memory B cells. The rise in IgM and IgG levels also rise later than the secondary response.

46
Q

What is the secondary response to T cell-dependent activation?

A

Since the body has memory of the pathogen the secondary response occurs much quicker and more forcefully.
- The production of IgG also occurs much faster, is higher, and lasts longer than the primary response.
- The antibodies that are produced by the secondary response are much more effective against the pathogen.

47
Q

What is the structure of IgM?

A

Has 10 different binding sites (looks like a snowflake).

48
Q

What is the structure of IgA?

A

Has four antigen binding sites and a secretory component (looks like a bone).

49
Q

What is neutralization?

A

antibodies bind to epitopes and neutralize them
- prevents virus from attaching to host cell and being able to enter the host cell
- can bind to flagella and stop motility, phagocytes destroy it

50
Q

What is opsonization?

A

giving a handle and helping with phagocytosis
- act as molecular handles that a macrophage can bind to
- makes it easier for macrophage to grab on, engulf and destroy the bacteria

51
Q

What is agglutination?

A

clumping
- turning the bacteria into a chain gang
- link bacteria together, stick them together to make it easier for phagocytes to grab on and destroy them