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Microbiology > Chapter 15 The Adaptive Immune Response > Flashcards

Chapter 15 The Adaptive Immune Response Flashcards

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Biology 101 flashcards
1
Q

Adaptive Immune Response

A
  • Can be acquired either naturally or artificially
  • Natural adaptive immunity: an organism or toxin enters the body and promotes an immune response
  • Artificial adaptive immunity: results from immunization with a vaccine
  • Both types are specific and have memory
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2
Q

Specific Immune Response

A
  • Immune response protects against one pathogen
  • Does not protect against other pathogens
  • Only exception is when two pathogens are very closely related
  • Example: Smallpox or Cowpox
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3
Q

Memory Immune Response

A
  • Results in a much stronger response upon re-exposure

- Long term immunity - possibly for life

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4
Q

Overview of Adaptive Immunity

A
  • Involves two general responses that respond against antigens
    Molecules that interact specifically with the adaptive immune system and elicit an adaptive response
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5
Q

Exogenous Antigens

A

Come from outside

- Example: Bacteria, Viruses, Toxins

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6
Q

Endogenous Antigens

A

Generated inside a body cell

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7
Q

Antibody Mediated Response (Humoral Response)

A

B cells

  • Detect exogenous antigens and proliferate to form plasm cells
  • Produce small protective molecules - antibodies (Ab)
  • Bind to the surface of bacteria, viruses, toxins, etc.
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8
Q

Cell Mediated Response

A

Helper T cells (TH)
- Direct and assist adaptive immunity and upregulate innate immunity
Cytotoxic T cells (Tc)
- Destroys abnormal body cells
- Example: Cells infected by viruses, and cancer cells

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9
Q

Antigen - Antibody Generator

A
  • Any molecule that induces antibody production, or binds to a specific receptor on a B or T cell
  • Each antibody recognizes only a small part of the antigen called an epitope (antigenic determinant)
  • A foreign particle (like a bacterial cell) has several antigens, and a vast array of potential epitopes
  • Some antigens are more immunogenic than others - Ex. Proteins often elicit a strong immune response
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10
Q

The Nature of Antibodies (Immunoglobulins)

A
  • Y shaped proteins that bind to antigens in a very specific manner
    Like a “Lock and Key”
    Only an antigen with the correct epitope will be bound
  • Each antibody binds to one and only one antigen
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11
Q

Antibody Structure

A
  • Each consists of 4 polypeptides - 2 light chains, and 2 heavy chains, and has 2 general parts:
    1) Two identical arms - Fab region (variable fragment)
  • Each with an identical antigen binding site specific for one epitope
    2) One Stem - Fc region (constant fragment)
  • Binds to complement proteins, phagocytes, etc, allowing the antibody to trigger other components of immunity
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12
Q

6 Protective Functions of Antibodies

A

1) Cross-linking (agglutination)
2) Neutralization
3) Complement Activation
4) Opsonization
5) Ab Dependent Cytotoxicity
6) Immobilization and Prevention of Adherence

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13
Q

Cross-linking (Agglutination)

A
  • Antigens get stuck together

- Reduces number of infectious units to be dealt with

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14
Q

Neutralization

A
  • Ab binds to and inactivates toxins, bacteria, viruses

- Blocks attachment sites

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15
Q

Complment Activation

A
  • Ab binds bacteria - acts as starting point for complement pathway
  • MAC attack
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16
Q

Opsonization

A

Ab flags down phagocytic cells - to engulf and destroy the antigen

17
Q

Ab Dependent Cytotoxicity

A

Ab flags down immune system cells to destroy abnormal or infected body cells

18
Q

Immobilization and Prevention of Adherence

A
  • Ab binds to flagella to stop pathogen from moving

- To pili to stop bacteria from colonizing

19
Q

5 Classes of Antibodies

A

1) IgG - Immunoglobulin G
2) IgM - Immunoglobulin M
3) IgA - Immunoglobulin A
4) IgD
5) IgE

20
Q

IgG - Immunoglobulin G

A
  • Most abundant
  • Binds to antigen very strongly
  • Found in the blood - but can also enter tissues in regions of inflammation
    Can cross placenta - confers passive immunity to fetus
21
Q

IgM - Immunoglobulin M

A
  • Consists of 5 units of Ab - a pentamer
  • Does not move as freely as IgG - IgM stays in the blood
    Often attached to surface of B cells
    -First Ab produced upon infection
  • Very good at cross-linking antigens
22
Q

IgA - Immunoglobulin A

A
  • Consists of 2 units of Ab - a dimer
  • Also known as secretory Ab
    Found in body secretions - saliva, mucous, tears, milk
  • Functions to protect mucosal surfaces
    Protects gastrointestinal tract of newborns
23
Q

IgD

A

Function unknown

24
Q

IgE

A
  • Found on the surface of certain immune system cells
  • Mast cells and Basophils
  • When it binds to antigens - the cell release histamine
    Attracts complement and phagocytes to the area.
    Histamine is responsible for allergy symptoms.
25
Q

B- lymphocytes (Cell of the Adaptive Immune System)

A

B cells

  • Antibody producing cells
  • Involved in humoral immune response
26
Q

T - lymphocytes (Cell of the Adaptive Immune System)

A

Helper T cells (Th cells)
-Help B and Tc cells prepare for an immune response
Cytotoxic T cells (Tc cells)
-Destroy abnormal body cells
- Ex. Cells infected by viruses and cancer cells

27
Q

Antigen Presenting Cells (APC)

A

Macrophages, B cells, dendritic cells

a) Foreign material (ex. bacterial cell) is engulfed by APC
b) Antigen is processes and presented to T cells along with self antigens
- Self antigens - part of major histocompatibility complex (MHC)
- Check to prevent destruction of our own cells by mistake
c) T cells become activated against the foreign material

28
Q

The B-Cells Response: Humoral Immunity

A
  • Each naive B cell carries Ig for one epitope on its surface
  • Circulates in blood, and gather in lymphoid organs
29
Q

If it encounters its specific epitope it will become activated

A
  • B cell receptor binds to the epitope on the antigen - Clonal Selection
  • Antigen is phagocytized
  • Antigen is digested into small fragments
  • Small fragments are presented on surface along with MHC class II to T-helper cells (Th)
  • If a Th recognizes the fragment as foreign, it activates the B cell to multiply and differentiate - B cell undergoes clonal expansion
30
Q

Clonal Expansion

A

The activated B cell divides and differentiates into:

1) Plasma Cells
2) Memory B cells

31
Q

Plasma Cells

A
  • Ab producing cells

- Short life span, produce a lot of Ab

32
Q

Memory B cells

A
  • Long living:20-30 years
  • Circulate in blood
  • If it encounters Ag again it will quickly multiply and change into Ab producing plasma cells
33
Q

Primary Response (Immunologic Memory)

A
  • B cells produce low levels of Ab
  • Slow process - takes 7-14 days
  • IgM first, followed by IgG and IgA
  • Major outcome: memory is built for the antigen
34
Q

Secondary Response (Immunologic Memory)

A
  • High levels of IgG
  • Fast response time: takes 1-2 days
  • Quickly overcomes the infection
  • Memory cells are replenished
35
Q

The T Cell Response: Cell- Mediated Immunity

A
  • Cytotoxic T cells (Tc) - Responsible for destroying abnormal cells
    Ex. Cells infected by viruses r bacteria, cancer cells, foreign cells
    Recognize antigens presented along with MHC class I
36
Q

T Cell Activation

A

a) A dendritic cell engulfs foreign antigen, presents antigen to a specific Tc
- Tc is activated to undergo clonal expansion
- Produces: Memory T cells and Cytotoxic T lymphocytes (CTLs)
b) Once the CTLs are activated - any body cell can serve as APC
c) Endogenous antigen is presented on the cell surface along with MHC class I
- CTL attaches to abnormal cell and releases:
1) Perforins - enzymes that poke holes in the abnormal cell’s membrane
2) Granzymes - enzymes that induce apoptosis (programmed cell death)

Microbiology (17 decks)

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