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Chapter 17 Flashcards

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1
Q

innate immunity

A

present at birth; nonspecific; no memory; rapid; halts infections; activated by interaction btw TLR (toll-like receptor) on cells in the body with PAMPs (pathogen-associated molecular patterns) on pathogens, which leads to infection.

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2
Q

adaptive immunity

A

acquired after exposure; specific; has memory; slower; clears infetion; activated by dendritic cells which sense the signal from innate immunity, activates T cells, which initiate adaptive immunity that leads to formation of antibodies and killer cells

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3
Q

B lymphocytes

A

arise and mature in bone marrow; involved in humoral immune responses (antibody immunity)

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4
Q

T lymphocytes

A

Arise in bone marrow, migrate to and mature in thymus, involved in cell-mediated immune responses

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5
Q

thymus

A

location of T cell maturation

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6
Q

bone marrow

A

location of B & T cell production, B cell maturation

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7
Q

antigen

A

sometimes interchangeable with immunogen. They are able to bind with specific antibodies; however, may or may not stimulate immune responses. Mostly proteins or large polysaccharides. Often components of invading microbes such as capsules, cell walls, flagella, fimbrae, and toxins of bacteria; the coats of viruses; surfaces of other types of microbes.

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8
Q

immunogen

A

can stimulate specific immune responses. Good: protein & polysaccharides. Poor: lipids, nucleic acids

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9
Q

epitope/antigenic determinants

A

region on antigen which antibody recognizes and interacts with.

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10
Q

hapten

A

small, simple molecules that are not immunogenic (do not stimulate immune response) unless combined with other miolecules; they may be recognized and bound by specific antibodies.

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11
Q

antibody

A

globular proteins (protein family with a compact globular form) - also called immunoglobins (Ig). Soluble proteins produced in response to immunogens and bind with specific antigens.

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12
Q

Structure of antibody: heavy & light chain, bridge, shape

A

has 2 heavy chains and 2 identical light chains, linked by disulfide bridges; forms a Y-shaped molecule.

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13
Q

Structure of antibody: constant region

A

lower parts of the 2 arms and the stem of the Y; same for all antibodies of the same class.

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14
Q

Structure of antibody: variable region

A

top portion of the 2 arms of the Y; has the antigen-binding sites that bind to epitopes; variable regions carry from antibody to antibody. Each Y-shaped molecule has 2 antigen-binding sites

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15
Q

Structure of antibody: variable region - antigen-binding site

A

formed by the heavy chains and the light chains

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16
Q

IgG

A

80%, most abundant in serum. Monomer; can cross placenta and protect fetus & newborns; enhances phagocytosis, neutralizes toxins & viruses

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17
Q

IgM

A

Pentamer structure; effective in causing agglutination (blood type test); mostly in blood; stays on B cell surface as receptor; first class of antibodies produced in primary response

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18
Q

IgA

A

Most abundant in the body - May be dimer or monomer; in secretions such as mucous, saliva, milk; prevent attachment of pathogens to mucousal surfaces

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19
Q

IgD

A

Monomer, on B cell surface; functions in initiating immune response

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20
Q

IgE

A

Monomer; bound to mast cells and basophil through their Fc (stem) regions; involved in allergic responses; increases during allergic reactions & parasitic infections

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21
Q

Role of B cells in humoral immunity

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A

antibodies are effective against pathogens that are circulating in the body, such as viruses and bacteria

22
Q

B cell activation

  1. Receptor
  2. Antigen
  3. MHC Class II
  4. Th cell > cytokines > B cells
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A

The B cell receptors (mostly IgM and IgD) recognize and bind to one particular epitope on antigen.

Antigen is engulfed and processed, fragmented.

MHC Class II (major histocompatibility complex) in the B cell bind to a fragment of antigen and display it on B cell surface.

T(h) cell receptor recognizes and interacts with the antigen-MHC Class II complex and is activated to produce cytokines, which activates B cells.

23
Q

B cell activation: Clonal selection

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A

Only one of the B cells with the receptors that recognize the particular epitope

24
Q

B cell activation: MHC class II

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A

Binds to a fragment of antigen and display it on B cell surface.

25
B cell activation: T(h) cell receptor
Recognizes and interacts with the antigen-MHC Class II complex and is activated to produce cytokines, which activates B cells.
26
Clonal expansion
activated B cells proliferate into a large clone of cells, which differentiate into plasma cells and memory cells. Each clone of B cells has the same specificity and only recognizes one specific antigen. Initial antibodies produced are IgM
27
Clonal expansion: plasma cells
antibody-producing cells; in general, short-lived.
28
Clonal expansion: memory cells
responsible for the faster, stronger secondary response; long-lived
29
Clonal expansion: T-dependent antigens
antigens that require help of T(h) cell for antibody production
30
Clonal expansion: T-independent antigen
Antigens that directly stimulate B cells to produce antibodies without the help of T(h) cell, characterized by repeating subunits, such as polysaccharides; provoke a weaker immune response than T-dependent antigens; no memory cells are generated.
31
Functions of antibodies: agglutination
basic monomer antibody (IgG), has 2 antigen-binding sites; can bind to 2 antigens; causes antigens to clump together, become insoluble, and precipitate; IgM has 10 antigen-binding sites (pentamer) and is a more effective aggluntanating molecule than IgG.
32
Functions of antibodies: opsonization
antibodies stimulate phagocytosis by binding to the antigen, such as the surface of a bacterial cell
33
Functions of antibodies: neutralization
antibodies block the activities of antigens, such as microbes and toxins by binding to them, preventing their attachment to the host cells
34
Functions of antibodies: activation of complement system
with the arms (antigen-binding sites) bound to the antigens, antibodies bind to the complement molecules via the stem region (Fc), activate a cascade of reactions by the complement system.
35
Functions of antibodies: antibody-dependent cell-mediated cytotoxicity
antibodies coat target cell (such as a worm), then macrophages, eosinophils, and the NK cells bind to the stem region (Fc) of antibodies. These cells of immune system then secrete substance to lyse the target cell.
36
Cellular immunity
protective function of immunization is associated with cells (CD4 cells, helper T cells)
37
humoral immunity
protective function of immunization is found in the humor (cell-free bodily fluid/serum)
38
Classes of T cells: T helper cells
CD4+ T cells--- recognize foreign antigen presented by MHC Class II on APCs (antigen presenting cells: macrophage, dendritic cell, B cell); activated T(h) cells produce cytokines that play roles in B cell activation, allergic reaction, inflammation, etc.
39
Classes of T cells: T cytotoxic cells
CD8+ cells ---recognize foreign antigen presented by MHC class I on APCs; activated Tc cells produce perforin and granzyme (pore-forming protein, protease that digests proteins) that lead to apoptosis (cell death) of targeted cells
40
Classes of T cells: T regulatory cells
formerly called T suppressor cells; CD4+ cells that also carry CD25; T(r) cells keep adaptive immunity in check; thus, prevent autoimmune disease, control inflammatory response, avoid targeting normal flora.
41
Antigen-presenting cells (APCs)
engulf a foreign antigen (pathogen) in tissue, process it, and present the antigen to T cells in lymph nodes or lymphoid tissues
42
APCs: B cells
Receptors (mostly IgM and IgD) recognize and bind to one particular epitode on antigen.
43
APCs: Dentritic cells
Can be found in lymph nodes, spleen, thymus, blood, skin, various tissues except brain; engulf pathogens in tissues and transport them to lymph nodes where the degraded fragments of pathogen are presented to T cells; dentritic cells are the principle APCs to induce T cell responses
44
APCs: macrophages
Involved in phagocytosis as discussed previously; take up and present the antigen to T cells
45
NK characteristics & role
innate; no specificity; need not to be stimulated by antigen; destroy virus-infected cells, cancer cells, parasites; kill target cell that does not express MHC class I self-antigens
46
Adaptive immunity: Naturally aquired active immunity
immunity conferred when person is infected with pathogens and recovered -- may last long time, even a life time (measles)
47
Adaptive immunity: Naturally acquired passive immunity
transfer of antibodies from a mother to her infant through placenta or breast milk, may last weeks or months
48
Adaptive immunity: Artificially acquired active immunity
result of vaccination, which is the introduction of antigens into the body; ex: killed/live weakened pathogens or inactivated bacterial toxins; provoke the body's immune response, long lasting protection
49
Adaptive immunity: Artificially acquired passive immunity
injection of antibodies into the body; immediate yet short-lived protection, only lasts a few weeks.
50
Active immunity
person's immune system responds after exposed to antigen
51
Passive immunity
person obtains antibodies produced by others

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