bio 156 chapter 14 powerpoint

8/14/2019 BIO 156 Chapter 14 Powerpoint

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BIO 156

Chapter 14


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The Immune System


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Viruses

Viruses are nonlivingbiological agents that

invade cells.

Viruses consist of

a nucleic acid core

a coat of protein

molecules called thecapsid.


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Viruses Are Grouped by Their Shape

Helical viruses have helical symmetry

Icosahedral viruses have isocahedral symmetry

Viruses that have both helical and icosahedral

symmetry have complex symmetry


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Rabies

Helical VirusHerpes, Icosahedral Virus

Smallpox

Complex Virus


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Bacteria Many bacteria perform usefulfunctions, while others cause

serious diseases.

Bacteria are classified living

organisms that reproduce on

their own without taking over

host cells.

Bacteria respond to

antibiotics although many

have become resistant tocommonly used antibiotics;

viruses do not, but new

antiviral drugs may help flu

sufferers.


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E. coli

S. aureus


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The Bodies First Line of Defense

In humans, the first line of defense is a physicaland chemical barrier.

Physical

the skin epithelial linings of the respiratory, digestive,

and urinary systems

Chemical

Body secretions that impair bacterial growth


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The bodys second line of defense combatsinfectious agents that penetrate the first line

and consists of cellular and chemical

responses.

Four nonspecific mechanisms include the

inflammatory response, pyrogens,

interferons, and complement.

The Bodies Second Line of Defense


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The Inflammatory Response

The inflammatory response involves

a chemical and cellular responses. Macrophages, cells derived fromthe monocyte, are found inconnective tissue beneath epithelia,where they phagocytize infectiousagents, preventing their spread.

Histamine, a chemical released by

damaged tissue, stimulates

arterioles in the infected tissue to

dilate.

The increase in blood flow raises

the temperature of the wound.

Heat stimulates macrophage

metabolism, accelerating the rate of

the destruction of infectious agents.


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The cells of the immune system, lymphocytes,selectively target foreign substances and foreignorganisms.

Lymphocytes circulate in the blood and lymphand take up residence in the lymphoid organs andlymphoid tissues.

The Third Line of Defense:

The Immune System

Substances that trigger an immune response

are large molecular weight molecules,particularly proteins and polysaccharides,

called antigens.

-Antigens are antibody-generating substances.


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Immature B and T cells are incapable of responding to

antigens but soon gain this ability.

B cells mature and differentiate in the bone marrow. T cells mature in the thymus.

B cells provide humoral immunity through the production of

antibodies. Antibodies are proteins that bind to specific antigens.

When T and B cells first encounter an antigen, the

primary response, they react slowly.

The rapidity of the secondary response is the result of theproduction of memory cells during the primary response.


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B cell Activation


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B cell Activation Continued


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Primary and Secondary Antibody Responses

Antibody Structure


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Antibodiesdestroy

antigens in one

of four ways:

Neutralization

Agglutination

Precipitation

Activation of thecomplement

system

How Antibodies Work


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T cells attack foreign cells directly.

T cells differentiate into at least four cell types, each

with a separate function in cell-mediated immunity.Cytotoxic T cellsMemory T cellsHelper T cells

Suppressor T cells

T cells


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The outer membrane of the tumor

cell (right) has been shot full of holes

by a protein, perforin, secreted from

the cytotoxic cell (left). The tumor

target cell has become leaky and aninflux of water has made it expand in

volume; it has also lost many of its

surface villi. In addition, there is a

large cavity in the membrane of the

tumor target cell.


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Macrophages play a very important role in humoral and cell-

mediated immunity.


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HIV


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HIV


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HIV


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Course of HIV Infection


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Kaposis Sarcoma


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Azidotheymidine (AZT) was the first drug used for

treatment

It interferes with reverse transcriptase activity

HIV can become resistant to some antivirals

This requires a cocktail of drugs called highly active antiretroviral

therapy (HAART)

HAART reduces the risk of HIV transmission and can extend life of

patients by about 8 years

A vaccine has not yet been developed

HIV continually mutates and recombines, making vaccinedevelopment difficult

A vaccine needs to activate T lymphocytes, which are the cells

infected by the virus


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HAART


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End of Chapter 14

bio 156 chapter 14 powerpoint

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