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Micro > Chapter 17 > Flashcards

Chapter 17 Flashcards

1
Q

adaptive immunity

A
  • also specific immunity or acquired immunity

- it is immunity that is adapted to a particular microbial invader or foreign substance

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2
Q

Humoral immunity (type of adaptive immunity)

A
  • involves the production of antibodies by the B-cells in response to a foreign invader
  • antibody mediated
    • B cells produce Ab in response to antigens
    • antibodies defend against bacteria, viruses and toxins that are circulating freely in the blood plasma
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3
Q

Cell-mediated immunity (type of adaptive immunity)

A
  • involves protection by activated T-cells
  • depends on T cells and does not use antibodies
  • response to invasion of intracellular bacteria and viruses located in phagocytic cells and infected cells, fungi, cancer cells and transplant tissue
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4
Q

naturally acquired (4 types of acquired (adaptive immunity)

A
  • active immunity- antigens enter body and the body produces Ab and activated T-cells
    • ex: Ag- bacteria and viruses
  • passive immunity- Ab pass from mother to fetus via the placenta or breast milk
  • mother is exposed to community diseases and makes Ab so fetus/ newborn is protected from the “current” disease in the community
  • first breast milk produced after birth, colostrum, has high concentration of Ab
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5
Q

Artificially acquired (4 types of acquired (adaptive) immunity)

A
  • active immunity- can receive vaccines and the body produces Ab and specialized lymphocytes
  • passive immunity- preformed Ab given as injection to provide temporary protection
  • Ab obtained from people who have had the disease and their body made Ab
  • short-term protection because the Ab break down after a period of time and are not replaced w/o another injection
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6
Q

vaccines

A
  • killed microbes (heat or chemicals)
  • toxoid- inactivated toxin
  • attenuated (weakened) live microbes
  • provide long-term protection
  • may need boosters
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7
Q

antigens

A
  • usually foreign substances
  • large molecules: M.W, > 10,000
  • antigenic determinants or epitopes are specific regions of the antigen that react w/ antibodies
    • example: bacterial cell has several epitopes on surface -> several types of Ab will be made against the bacterial cell
  • smaller molecules do not stimulate Ab production but can combine w/ a larger molecule such as a protein and stimulate Ab production
    • ex of Ag: bacterial capsules, cell walls, flagella, fimbriae
    • viral capsid and envelope
    • pollen transplanted tissue
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8
Q

Hapten (antigen)

A

low M.W. molecule that isn’t antigenic unless combined w/ a carrier molecule

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9
Q

antibodies

A
  • antibody= immunoglobin
  • antibody is a large protein molecule produced by B cells in response to the presence of an antigen
  • are highly specific and can combine w/ the type of antigen that stimulated its production
  • Ab neutralize or help destroy the Ag
  • very specific and only bind to one type of Ag
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10
Q

Antibodies (4 polypeptide chains)

A
  • 2 identical heavy chains
  • 2 identical light chains
  • chains linked with disulfide bonds (-S-S-)
  • variable region- unique for the Ag that the Ab binds to
  • constant region same for all of a persons Ab
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11
Q

five classes

A
  • IgG
  • IgM
  • IgA
  • IgD
  • IgE

-some are monomers, dimers and pentamers

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12
Q

development of B and T cells

A
  • both develop from stem cells in bone marrow (adult) and liver (fetus)
  • site of final maturation determines which type of cell will be produced
    • stem cells that migrate to the thymus become T-cells
    • cells that remain in the bone marrow become B-cells
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13
Q

B-cells

A
  • mature B-cell has about 100,000 IgM and IgD antibodies on the surface of the cell
  • mature B cells migrate to the lymph nodes and spleen
  • these Ab are specific for the same epitope
  • when the Ab detect and bind with the Ag for which they are specific, B cell is activated
  • activated C cell undergo clonal expansion or proliferation
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14
Q

activation of B cells

A
  • all cells in the body have markers that identify the cell as belonging to the host. sometimes called “self” markers
  • molecules are called major histocompatibility complex (MHC)
    • MCH II found on antigen presenting cells- those cells that phagocytosize antigens and embed pieces of the antigen in their cell membrane
    • MHC I- found on other cells in the body

-the B cell that is activated by the AG will engulf the antigen and present the Ag on the cell membrane with the MHC II

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15
Q

activation of B cells cont.

A
  • the receptor on the T helper cell recognizes the MHCII + Ag fragment and is activated
  • T helper needs both the Ag and MHC II for activation
  • T helper produces cytokines (chemical messengers) which in turn activate the B cell
  • activated B cell begins clonal expansion
  • some B cells mature into plasma cells which produce Ab
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16
Q

Clonal selection

A

-stem cells -> B cells
-B cells are each specific for one antigen
-millions of diff B cells specific for one type of antigen
when the B cell attaches to the antigen for which it is specific, the B cell becomes activated
-cell divides
-some cells become long-lived memory cells which will detect the antigen in the future
-some B cells proliferate into plasma cells
-plasma cells secrete large amounts of Ab specific for the antigen
-secrete 2000 Ab per second
-plasma cell lives only a few days

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17
Q

clonal selection :end

A
  • some B cells and T cells may become sensitized against the hosts own cells; they do not have self tolerance
  • in these cases the B and T cells do not recognize “self”
  • B and T cells are destroyed by a process called clonal deletion
18
Q

apoptosis

A
  • Human body makes 100 million lymphocytes/day so an equal number must die
  • B cells that do not encounter an antigen under go programmed cell death: called apoptosis

Some diseases are linked to malfunctions of apoptosis
AIDS –excess apoptosis
Leukemia – too little apoptosis

19
Q

capases (apoptosis)

A

family of enzymes responsible

20
Q

cell death (apoptosis)

A

genome cut into pieces; membranes bulge called blebbing

21
Q

outcomes of Ab-Ag binding

A
  • Agglutination
  • Opsonization
  • Antibody-dependent cell-mediated cytotoxicity
  • Neutralization
  • Activation of complement
  • Inflammation – due to complement

See Figure

22
Q

immunological memory

A

-Ab titer is the concentration of Ab in the serum

-Primary response:
Takes a few days for Ab to be produced
First Ab produced is IgM; second produced is IgG
Then gradual decline in titer

-Secondary response
Anamnestic response
After 2nd exposure
Due to memory B cells
Quicker response and higher levels of IgG Ab produced
May occur weeks, months or years later
23
Q

monoclonal Ab

A
  • Culture of cells that produce only one type of antibody
  • Normally would get a mix of B cells producing a mix of Ab if just sampled the spleen
  • Made from hybridomas: myeloma cells + spleen cells (which have some B cells mixed in)
  • Monoclonal Ab called Mabs
  • Originally made with mouse cells so there were allergic reactions
  • Goal to make fully human antibodies
  • Having a source Ab that is pure has enabled rapid tests to be developed for the clinical diagnostic lab
  • Pure Ab produced by the hybridomas

Examples:
Pregnancy test
Diagnosis of disease

24
Q

T cells and Cell-mediated immunity

A
  • Involves specialized lymphocytes, primarily T cells, that respond to intracellular antigens
  • Defends against bacteria and viruses that have invaded cells, fungi, protozoans, helminths (parasites), tissue grafts, and cancer cells
  • Cytokines – chemical messengers produced by T cells
25
Q

cytokines

A

-chemical messengers produced by T cells

26
Q

4 main functional groups of cells

A

Helper T cells – central role in immune response, TH

Cytotoxic T cells – destroy target cells on contact, TC

Delayed hypersensitivity T cells – certain allergic reactions

Suppressor T cells – turn off immune response when antigen not present

Can also classify the cells based on cell-surface receptor, CD -clusters of differentiation

CD4 cells are primarily helper T cells and include the long-lived memory cells

CD8 cells become cytotoxic T lymphocytes

27
Q

development of T cells

A
  • T cells develop from stem cells in the bone marrow or fetal liver
  • The stem cells migrate to the thymus where they differentiate into T cells
  • T cells then migrate to the lymph nodes, spleen and lymph system and the Peyer’s patches of the gastrointestional tract
  • Peyer’s patches are secondary lymph tissue
28
Q

Cytokines

A
  • Chemical messengers produced by T cells
  • Interleukins- communication between white blood cells
  • Interferons – protect cells against viral infections
  • Chemokines – induce migration of leukocytes into infected areas
  • TNF – tumor necrosis factor – involved in inflammatory response
29
Q

T cells and Antigen Presenting cells

A
  • T cells recognize antigens only when they have been processed by an antigen presenting cell, APC
  • APC include macrophage, dendritic cells, and B cells
  • Cell engulfs the antigen, digests it into pieces, and combines the pieces with the MHC II molecules on the cell membrane
30
Q

antigen presenting cells -APC’s

A
  • Three types of cells can serve as APC’s
    • B cells
    • Macrophage
    • Dendritic cells
  • The antigens are presented with MHC II receptors on the cell surface
  • Antigen presentation necessary to activate T cells
31
Q

T-cells and Antigen Presenting Cells

A
  • TH, T helper cells (CD4 T cells) have receptors on the cell surface
  • The TH cells have been sensitized to a specific antigen
  • The TH cell receptor encounters the Ag-MHC II complex, it binds
  • The APC produces a cytokine that stimulates the T cell and then the T cell produces cytokines of its own
  • T cell proliferates to produce memory cells and effector cells (another term for “functional” cells)
32
Q

T helper cells

A
  • After activation the TH cells differentiate into TH1 cells, TH2 cells, and memory cells
  • TH 1 cells – activate cells in cellular immunity
    • Macrophage
    • CD8 cells (cytotoxic cells)
    • Natural killer cells
  • TH2 cells – produce cytokines related to allergic reactions and parasitic infections
33
Q

Cytotoxic T cells

A
  • Cytotoxic T cells, CD8, are precursors to cytotoxic T lumphocytes, CTLs
  • A CTL is an effector cell that attacks cells that are “non-self”
  • Examples of non-self cells are cells infected by bacteria and viruses, tumor cells, and transplanted tissue cells
  • After the cytotoxic T cell, CD8, detects the antigen-MHC I complex on the cell surface, it differentiates into a CTL
34
Q

Cytotoxic T cells cont.

A
  • The CTL attaches to the target cell and releases a pore-forming protein, perforin
  • Perforin causes a hole to form in the target cell
  • Granzymes, protease enzymes that cause apoptosis, enter target cell through pore
  • Apoptosiss occurs
35
Q

both T and B lymphocytes divide

A
  • B cells -> plasma cells + memory cells

- T cells -> activate T cells + memory cells

36
Q

Humeral vs. Cell-mediated immunity

A
  • activated B cells -> plasma cells -? produce Ab against original Ab
  • activated T cells -> regulate and participate in specific immune response
37
Q

Products of B lymphocytes : Antibody Structure and Functions

A
  • Progeny of dividing B-cell clone are
    • plasma cells -> antibodies
    • B memory cell
    • B regulatory cells
  • plasma cells programmed to synthesize and secrete antibodies into tissue fluid and blood
  • when antibodies attach to antigen, the antigen is marked for destruction or neutralization
  • humeral immunity
38
Q

How T cells Respond to Antigen: cell mediated immunity (CMI)

A
  • when activated by antigen, T cell gives rise to one of three different types of progeny
    • Th1 cells- activate macrophages and help Tc cells
    • Tb2 cells- assist B-cell processes
    • Tc cells- lead to the destruction of infected host cells and other “foreign cells”
    • plus T regulatory and T memory cells
39
Q

Epitope (antigens: size and shape)

A
  • portion of the antigen (amino acids) recognized by lymphocyte receptor
  • large foreign objects such as bacteria may have several types of antigenic determinants on them (flagella, capsule, cell surface)
40
Q

Haptens (antigens: size and shape)

A

-antigens that are too small to elicit an immune response

41
Q

antigen presenting cells - APC’s

A
  • during B cell activation, the B cell engulfed the antigen and “presented” the antigen on the cell surface
  • the T cell recognized the “presented” antigen and was activated
  • in most immune reactions, the antigen must be presented to the lymphocyte
42
Q

3 types of cells that can serve as APC’s

A
    1. B cells
    1. Macrophage
  • 3.dendritic cells
  • antigens are presented with MHC II receptors on the cell surface
  • antigen presentation necessary to activate T cells

Micro (18 decks)

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