unit 31 immune system
TRANSCRIPT
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31.1 Pathogens and Human Illness
KEY CONCEPTGerms cause many diseases in humans.
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31.1 Pathogens and Human Illness
Germ theory states that microscopic particles cause certain diseases.
• Germ theory proposes that microorganisms cause diseases.– proposed by Louis Pasteur– led to rapid advances in understanding disease
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31.1 Pathogens and Human Illness
• Disease-causing agents are called pathogens.
• Koch’s postulates support the theory.
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31.1 Pathogens and Human Illness
There are different types of pathogens.
• Bacteria are single-celled organisms. – cause illness by destroying
cells – release toxic chemicals
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31.1 Pathogens and Human Illness
• Viruses are genetic material surrounded by a protein coat.– force host cells to
make more viruses – very small
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31.1 Pathogens and Human Illness
• Fungi can be multicellular or single-celled.
– take nutrients from host cells– occur in warm and damp places
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31.1 Pathogens and Human Illness
• Protozoa are single-celled organisms.
– use host cells to complete their life cycles– take nutrients from host cell
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31.1 Pathogens and Human Illness
• Parasites are multicellular organisms.
– grow and feed on a host – possibly kill the host
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31.1 Pathogens and Human Illness
• Different pathogen cause common infectious diseases.
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31.1 Pathogens and Human Illness
Pathogens can enter the body in different ways.
• Pathogens can be transferred by direct or indirect contact.• Indirect contact does not require touching an infected
individual.
– touching an infected surface– breathing in infected air
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31.1 Pathogens and Human Illness
• Vectors carry a pathogen and transmit it into healthy cells.
• Direct contact requires touching an infected individual. Includes: – kissing– sexual intercourse – hand shaking
tick
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31.2 Immune System
KEY CONCEPTThe immune systems consists of organs, cells, and molecules that fight infections.
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31.2 Immune System
Many body systems protect you from pathogens.
• The immune system is the body system that fights off infection and pathogens.
• Many other tissues and systems help the immune system.– Skin is a physical barrier to infection.– Mucous membranes trap pathogens entering the body.– The circulatory system transports immune cells.
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31.2 Immune System
Cells and proteins fight the body’s infections.
• White blood cells attack infections inside the body.– Phagocytes engulf and destroy pathogens. – T cells destroy infected cells.– B cells produce antibodies.
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31.2 Immune System
• Three types of proteins fight off invading pathogens.
– Complement proteins weaken pathogen membranes.– Antibodies make pathogens ineffective. – Interferons prevent viruses from infecting healthy cells.
antibody
pathogens
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31.2 Immune System
Immunity prevents a person from getting sick from a pathogen.
• In all immunity, pathogens are destroyed before you get sick.
• Passive immunity occurs withoutan immune response.– mother’s milk– genetics
• Active immunity occurs after aspecific immune response
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31.3 Immune Responses
KEY CONCEPTThe immune system has many responses to pathogens and foreign cells.
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31.3 Immune Responses
Many body systems work to produce nonspecific responses.
• Nonspecific responses are the same for every pathogen.• In inflammation, blood vessels become leaky.
– white blood cells movetoward infection anddamaged tissue
– characterized by swelling, redness, and pain
capillary wallextracellular space
white blood cell
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31.3 Immune Responses
• In fever, body temperature increases.
– High fevers can cause seizure, brain damage, and even death.
– Low fevers stimulate white blood cells to mature.
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31.3 Immune Responses
Cells of the immune system produce specific responses.
• Specific immune responses begin with the detection of antigens.– Antigens are surface proteins on pathogens.– Each pathogen has a different antigen.
virus
antigens
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31.3 Immune Responses
pathogen
antigens
T cell
receptors activated T cells
antigens
memory T cells
• There are two specific immune responses.– Cellular immunity uses T cells to destroy infected body
cells.
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31.3 Immune Responses
• There are two specific immune responses.– Humoral immunity uses B cells to produce antibodies.
memory B cells
activated B cells
antibodies
B cell
T cell
pathogen
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31.3 Immune Responses
• Both responses produce memory cells.
– specialized T and B cells– provide acquired (active) immunity
B cellT cell
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31.3 Immune Responses
The immune system rejects foreign tissues.
• Tissue rejection occurs in organ or tissue transplants.• Tissue rejection is the result of an immune response.
– immune system detects protein markers on the donor tissue
– makes antibodies against the donor’s tissue
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31.4 Immunity and Technology
KEY CONCEPTLiving in a clean environment and building immunity help keep a person healthy.
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31.4 Immunity and Technology
Many methods are used to control pathogens.
• Antibiotics and antiseptics cause pathogens to burst.
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31.4 Immunity and Technology
• Antiseptics kill pathogens outside of the body.– do not target specific pathogens– examples include vinegar and soap
• Antibiotics kill pathogens inside the body.– target one specific bacterium or fungus– not effective against viruses
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31.4 Immunity and Technology
• Antibiotic resistance can cause medicines to become ineffective.– Some bacteria in a population have genes that make
them immune to antibiotics.– These bacteria spread the gene, making the antibiotics
useless.
A bacterium carriesgenes for antibioticresistance on a plasmid.
A copy of the plasmid is transferredthrough conjugation.
Resistance is quicklyspread throughmany bacteria.
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31.4 Immunity and Technology
Vaccines artificially produce acquired immunity.
• Vaccines also control pathogens and disease.– given to prevent illness– contain the antigen of a weakened pathogen
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31.4 Immunity and Technology
• Vaccination provides immunity.– stimulates a specific
immune response
– allows immune system to respond quickly to infection
– causes memory cells to be produced
– has such a fast response, a person will not get sick
A memory B cell isstimulated when the real pathogen binds to it.
2
The B cell quickly activates and makes antibodies that fight the pathogens before you get sick.
3
Antigens in a vaccinetrigger an immune response, and memory B cells are made.
1memory B cells
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31.5 Overreactions of the Immune System
KEY CONCEPTAn overactive immune system can make the body very unhealthy.
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31.5 Overreactions of the Immune System
Allergies occur when the immune system responds to harmless antigens.
• An allergy is an response to a harmless antigen.• Allergies are caused by allergens.
– Allergens are antigens that cause an allergic reaction.– Allergens cause inflammation responses.
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31.5 Overreactions of the Immune System
• There are many different allergens. – food, e.g. peanuts,
milk, wheat, etc.– airborne, e.g. pollen,
dust mite feces, mold, etc.
– chemical, e.g. nickel, medicine, bee stings, etc.
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31.5 Overreactions of the Immune System
• Allergens can cause anaphylaxis. – Anaphylaxis is an extreme inflammation response.– Blood vessels and airways become too porous.– If not treated immediately, anaphylaxis can cause death.
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31.5 Overreactions of the Immune System
In autoimmune diseases, white blood cells attack the body’s healthy cells.
• Autoimmune diseases are failures of the immune system.– White blood cells cannot recognize healthy cells.– White blood cells attack healthy body cells.– Tissues fail because of attack.
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31.5 Overreactions of the Immune System
• There are over 60 autoimmune diseases.
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31.6 Diseases that Weaken the Immune System
KEY CONCEPTWhen the immune system is weakened, the body cannot fight off disease.
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31.6 Diseases that Weaken the Immune System
Leukemia is characterized by abnormal white blood cells.
– characterized by immature white blood cells – causes weakened immune system
• Leukemia is cancer of the bone marrow.
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31.6 Diseases that Weaken the Immune System
• Leukemia leads to opportunistic infections.– occur because white blood cells cannot fight infections– if immune system were healthy, would fight these
infections
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31.6 Diseases that Weaken the Immune System
HIV targets the immune system.
• The human immunodeficiency virus (HIV) is a retrovirus. – attacks and weakens the
immune system– is transmitted by mixing
infected blood with a bodily fluid
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31.6 Diseases that Weaken the Immune System
• HIV infection leads to AIDS.
HIV
T celldeadT cell
antibody
activatedB cell
– HIV reproduces in and destroys T cells.– The body cannot replace T cells fast enough.– T cells cannot help in immune responses.
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31.6 Diseases that Weaken the Immune System
• AIDS is acquired immune deficiency syndrome. – several opportunistic infections– very low amount of T cells