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Biology 228: Microbiology > Chapter 18 > Flashcards

Chapter 18 Flashcards

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1
Q

What two important characteristics are adaptive immunity defined by?

A

Specificity and memory.

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2
Q

Primary immunity response versus secondary immunity response.

A

First exposure to antigen -> primary
Subsequent exposure stimulates a faster and stronger response -> secondary.

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3
Q

What are the dual immunity systems of adaptive immunity?

A

Humoral immunity and cellular immunity.

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4
Q

What is humoral immunity?

A

Antibodies produced by B cells.

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5
Q

What is cellular immunity?

A

T cells directed against intracellular pathogens.

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6
Q

What are antigens (immunogens)?

A

Molecules that activate adaptive immunity. Antigen possesses smaller epitopes.

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7
Q

What are epitopes?

A

Each capable of inducing a specific adaptive immune response.

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8
Q

What does an antigen’s ability to stimulate an immune response depend on?

A

Molecular class, molecular complexity, and size.

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9
Q

What are haptens?

A

Free epitopes that are not part of the complex three-dimensional structure of a larger antigen.

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10
Q

How can haptens become antigenic?

A

They must attach to a larger carrier molecule (usually a protein) to produce a conjugate antigen.

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11
Q

What are antibodies (immunoglobulins)?

A

Y-shaped glycoproteins with two Fab sites for binding antigens and an Fc portion involved in complement activation and opsonization.

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12
Q

What are the five classes of antibody (heavy chain)?

A

IgM, IgG, IgA, IgE, and IgD.
They differ in size, arrangement, location within the body, and function.

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13
Q

What is the function of IgG monomers?

A

Binds to phagocytes.
Neutralization, agglutination, compliment activation, opsonization, and antibody-dependent cell-mediated cytotoxicity.

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14
Q

What is the function of IgM pentamers?

A

Neutralization, agglutination, and complement activation. The monomer form serves as the B-cell receptor.

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15
Q

What is the function of secretory IgA dimer?

A

Neutralization and trapping of pathogens in mucus.

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16
Q

What is the function of the IgD monomer?

A

B-cell receptor.

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17
Q

What is the function of the IgE monomer?

A

Binds to mast cells and basophils.
Activation of basophils and mast cells against parasites and allergens.

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18
Q

What are the five primary functions of antibodies?

A
  1. Neutralization
  2. Opsonization
  3. Agglutination
  4. Compliment activation
  5. Antibody-dependent cell-mediated cytotoxicity (ADCC)
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19
Q

What is the major histocompatibility complex (MHC)?

A

A collection of genes coding for glycoprotein molecules expressed on the surface of all nucleated cells.

20
Q

What are MHC I molecules?

A
  • expressed on all nucleated cells
  • essential for the presentation of normal “self” antigens.
  • Cells that become infected by intracellular pathogens can present foreign antigens on MHC I as well, marking the infected cell for destruction.
21
Q

What are MHC II molecules?

A
  • expressed only on the surface of antigen-presenting cells (macrophages, dendritic cells, and B cells).
  • Antigen presentation with MHC II is essential for the activation of T cells.
22
Q

What do antigen-presenting cells (APCs) do?

A

Primarily ingest pathogens by phagocytosis, destroy them in the phagolysosomes, process the protein antigens, and select the most antigenic/immunodominant epitopes with MHC II for presentation to T cells.

23
Q

What is cross-presentation?

A

a mechanism of antigen presentation and T-cell activation used by dendritic cells not directly infected by the pathogen; it involves phagocytosis of the pathogen but presentation on MHC I rather than MHC II.

24
Q

Where are immature T lymphocytes produced?

A

In the red bone marrow and travel to the thymus for maturation.

25
Q

What is thymic selection?

A

A three-step process of negative and positive selection that determines which T cells will mature and exit the thymus into the peripheral bloodstream.

26
Q

What is central tolerance?

A

Involves negative selection of self-reactive T cells in the thymus.

27
Q

What is peripheral tolerance?

A

Involves energy and regulatory T cells that prevent self-reactive immune response and autoimmunity.

28
Q

What are the three classes of T cells?

A

Helper T cells, cytotoxic T cells, and regulatory T cells.

29
Q

What is the T-Cell Receptor (TCR)?

A

Similar in structure to immunoglobulins, but less complex. Millions of unique epitope-binding TCRs are encoded.

30
Q

What are helper T cells?

A

CD4
MHC II
Orchestrate humoral and cellular immunity.
Involved in the activation of macrophages and NK cells.

31
Q

What are regulatory T cells?

A

CD4
MHC II
Involved in peripheral tolerance and prevention of autoimmune responses.

32
Q

What are cytotoxic T cells?

A

CD8
MHC I
Destroy cells infected with intracellular pathogens.

33
Q

What subtypes do helper T cells differentiate into?

A

TH1, TH2, TH17, and memory T cells.

34
Q

How is differentiation directed?

A

By the specific cytokines to which they are exposed.

35
Q

What do TH1, TH2, and TH17 do?

A

Perform different functions related to stimulation of adaptive and innate immune defenses.

36
Q

What are memory T cells?

A

Long-lived cells that can respond quickly to secondary exposures.

37
Q

What are the functions of TH1 cells?

A
  • Stimulate cytotoxic T cells and produce memory cytotoxic T cells
  • Stimulate macrophages and neutrophils (PMNs) for more effective intracellular killing of pathogens
  • Stimulate NK cells to kill more effectively
38
Q

What are the functions of TH2 cells?

A
  • Stimulate B cell activation and differentiation into plasma cells and memory B cells
  • Direct antibody class switching in B cells
39
Q

What is the function of TH17 cells?

A

Stimulate immunity to specific infections such as chronic mucocutaneous infections.

40
Q

What is the function of memory T cells?

A

“Remember” a specific pathogen and mount a strong, rapid secondary response upon re-exposure.

41
Q

What do cytotoxic T cells do?

A

Target and kill cells infected with intracellular pathogens. Killing requires recognition of specific pathogen epitopes presented on the cell surface using MHC I molecules. Killing is mediated by perforin and granzymes that induce apoptosis.

42
Q

What do B lymphocytes or B cells do?

A

Produce antibodies involved in humoral immunity.

43
Q

Where are B cells produced?

A

Produced in the bone marrow, where the initial stages of maturation occur -> move to the spleen for final steps of maturation into naive mature B cells.

44
Q

What are B-cell receptors (BCRs)?

A

Membrane bound monomeric forms of IgD and IgM that bind specific antigen epitopes with their Fab antigen binding regions.

45
Q

What are T-dependent antigens?

A

They can only activate B cells with the cooperation of helper T cells.

46
Q

What are T-independent antigens?

A

Do not require T cell cooperation.

47
Q

What does T cell-dependent activation of B cells involve?

A

Processing and presentation of protein antigens to helper T cells, activation of the B cells by cytokines secreted from activated TH2 cells, and plasma cells that produce different classes of antibodies as a result of class switching.
- Memory B cells are also produced

Biology 228: Microbiology (20 decks)

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