causes: germ theory of disease led by louis pasteur (french) and robert koch (german) bacteriologist...

Immune System and Disease

Infectious DiseaseCauses:

Germ Theory of Disease• Led by Louis Pasteur (French) and Robert Koch

(German) bacteriologist Infectious Disease – Occurs when microorganisms cause physiological changes that disrupt normal body functions

Agents of Disease

Infectious diseases can be caused by viruses, bacteria, fungi, protozoa, worms of various types, and parasites.

Pathogens – Any living organism or virus that is capable of causing a disease

Agents of DiseaseOur bodies are too well defended for most pathogens to enter our bodies

In case they do enter we have often previously developed an immunity to that pathogen For bacteria there are chemicals that work against bacteria called antibiotics

Agents of Disease

Viruses• Characteristics• Nonliving• Replicate by inserting their genetic material into a

host cell and taking over many of the host cell’s function

• Diseases• Common cold• Influenza• Chicken pox • Warts

Agents of DiseaseBacteria

• Characteristics• Break down the tissues of an infected organism for

food or release toxins that interfere with normal activity in the host

• Disease• Streptococcus infection (Strept Throat)• Diphtheria• Botulism• Anthrax

Agents of Disease

Fungi• Characteristics• Cause infections on the surface of the skin, mouth,

throat, fingernails, and toenails.• Dangerous infection may spread from lungs to

other organs• Disease• Ringworm• Thrush

Agents of DiseaseProtozoa

• Characteristics• Single-celled Eukaryotes may infect people through

contaminated water and insect bites• They take nutrients from their host• Most inflict damage to cells and tissue

• Disease• Malaria• African Sleeping Sickness• Intestinal Diseases

Agents of DiseaseParasitic Worms

• Characteristics• Most that infect humans are wormlike • May enter through the mouth, nose, anus, or skin• Most reside in the intestinal tract where they

absorb nutrients from the host• Diseases• Trichinosis• Schistosomiasis• Hook worm• Elephantiasis

How Diseases SpreadPathogens often spread by the symptoms of the actual disease

Sneezing, coughing, or diarrheaNatural selection favors the pathogens with adaptations that help them spread from host to host

Coughing, Sneezing, and Physical ContactUsually bacteria or viruses that infect the nose, throat, or respiratory tract

Spread by indirect contactCoughing and sneezing releases thousands of tiny droplets that can be inhaled by other people

Droplets can settle on objects, you touch them then touch your nose or mouth

Coughing, Sneezing, and Physical Contact

Pathogens like staphylococci (staph) are drug resistant and are transferred by body to body contact or by towel or sports equipmentPrevention

Exchange of Body Fluids

Sexual Transmitted Disease – pathogens transmitted by sexual activity, need direct contact from body to bodyInclude: • Herpes• Gonorrhea• Syphilis • Chlamydia

Exchange of Body Fluids

Other pathogens need blood to blood contact often seen with IV drug user

HepatitisHIV can be both transmitted by both blood and sexual contact.

Contaminated Water or FoodMany pathogens that infect the digestive tract are spread through the water contaminated by feces from infected people or animalsSymptoms of these diseases include diarrhea

Adaptation that helps spread pathogenContaminated water can be consumed or spread on fruits or vegetables

Prevention is as simple as washing foods

Contaminated Water or Food

Bacteria can be present in seafood and uncooked meat

Cooking properly can prevent diseases caused by these pathogens

Zoonosis: The Animal Connection

Zoonosis – any disease that can be transmitted from animals to humans• Mad Cow Disease• SARS (Severe Acute Respiratory Syndrome)• West Nile Virus• Lyme Disease• Ebola• Bird Flu

The Animal ConnectionVectors – a carrier of a pathogen that transports the pathogen but does not get sick itself• Infection can also occur when a person is bitten

by an infected animal• Consumes the meat of an infected animal• Come in close contact with an infected animal’s

waste or secretions

Preventing Pathogens From Entering Our Bodies

The best way to prevent disease is to prevent pathogens from causing diseases

Stay away from sources of infectionMain reason why we still quarantine (isolate) people with transmittable disease

Defense Against InfectionNonspecific Infection

1st Line of Defense• Skin – widespread physical barrier• Two primary layers:1. Dermis – Alive (on the bottom)• Contains: sweat glands, capillaries, sensory

receptors, and dermal cells that give structure and strength to skin

2. Epidermis – mostly dead (on top)• Dermal cells die and are moved up• This dead layer is a good barrier against most

pathogens (can’t infect a dead cell??)


1st Line of Defense• Skin• As long as skin stays intact you are protected from

pathogens entering living tissues• This is why it is important to cleans and cover cuts

and abrasions


1st Line of Defense• Stomach Acid• Stomach secretions destroy many swallowed pathogens• Acidic environment of the stomach helps to kill most ingested

pathogens

Defense Against Infection1st Line of Defense• Mucus • Saliva, mucus, and tears protect openings such as

mouth, nose, and eyes• Cells of mucus membrane secrete mucus• Sticky substance that can trap pathogens• This prevents pathogens from reaching cells they could

infect• Lysozyme - an enzyme contained in saliva mucus and tears• Break down bacterial cell walls

• Cilia hair like structures that helps capture pathogens

Defense Against Infection1st Line of Defense• Mucus• Some areas of mucous membranes:

• Trachea – tube which carries air to and from lungs• Nasal Passages – tubes that allow air to enter the nose

and then the trachea• Urethra – tube that carries urine from bladder to the outside• Vagina – reproductive tract leading from uterus to the outside

Defense Against Infection• 2nd Line of Defense• Inflammatory Response • Infected area become red and painful or

inflamed• Response begins when pathogens stimulate cells

called Mast Cells• Mast Cells release chemicals known as

Histamines

Defense Against Infection2nd Line of Defense

Histamines• Increase blood flow and fluids to the affected area• Causes swelling in the infected area• White blood cells move in

Leucocytes (AKA white blood cells)• Cells in our bloodstream that help fight off pathogens• Also provide immunity for pathogens we encounter the

second time Phagocytes – engulf and destroy bacteria (type of leucocyte)

Defense Against Infection2nd Line of Defense

Macrophages - Large white blood cells that are able to change their cellular shape to surround an invader (also a leucocyte)

• It is not unusual for a macrophage to encounter an invader outside the blood stream

All the above causes an increase in temperature in the area

Defense Against Infection• 2nd Line of DefenseInterferons• Proteins (produced by host cells) that inhibit

synthesis of viral proteins• This is a way of “buying time” for a specific immune

response

Defense Against Infection• 2nd Line of DefenseFever• Increased body temperature slows down or

stops the growth of some pathogens• Also speeds up the immune response• Fever caused by chemicals released by immune

system

Specific Defenses: The Immune ResponseResponds to particular pathogens

Recognizing “Self”• A healthy immune system recognizes all cells and

proteins that belong in the body; as selfRecognizing “Nonself”

• The immune system recognizes foreign organisms and molecules as other or “nonself”.

• Once recognized as “nonself” it uses cellular and chemical weapons to attack them

• Recognition is based on the protein molecules that make up part of the surface of all cells and viruses • This is a “nonspecific” response because the ID of the

pathogen has not been established just “not self”

Specific Defenses: The Immune ResponseImmune Response – after an encounter with specific invader the immune system remembers it• This enables a more rapid response if invaded

by the same pathogen

Specific Defenses: The Immune Response

Antigens – any foreign substance that can stimulate an immune response• Caused by proteins located on the outer surface

of bacteria, viruses, or parasites• The immune system response to antigens by:1. Increase the number of cells that attack the

invader directly2. Produce antibodies• Proteins that “tag” antigens for destruction• Antibodies are produced for a specific type of

pathogen

Specific Defenses: The Immune Response• Each antibody is different and specific for each

antigen• Still very similar in structure• Each antibody is a Y shaped protein

Binding Site

Specific Defenses: The Immune ResponseLymphocytes

B Lymphocytes (B Cells)• Produced and mature in red bone marrowT Lymphocytes (T Cells)• Produced in bone marrow but mature in thymus

• Each recognizes one specific antigen• Our gene determine particular B/T Cells• When mature both types of cells travel to lymph

nodes and spleen, where they encounter antigens

Lymphocyte

Many different types of lymphocytes exist.Each recognizes one specific antigen and responds by dividing to form a clone.This clone then secretes a specific antibody against the antigen.

Fighting Infectious DiseaseAcquired Immunity

Vaccination - the injection of a weakened form of a pathogen or of a similar but less dangerous pathogen to produce immunity

Fighting Infectious DiseaseAntibodies work because:

Bacteria are prokaryotic Body cells are Eukaryotic There are differences in biochemical reaction and pathways

Antibiotics take advantage of these difference

Fighting Infectious DiseaseThere are different types of bacteria:

One might stop protein synthesis in bacteriaStill have no effect in normal cells ability to synthesis bacteria (Affect metabolic pathways)

One type may inhibit the production of a new cell wall by bacteria

Cell cannot grow and divide

Fighting Infectious DiseaseViruses use our own body cells’ metabolism to create new viruses.

Any chemical that would inhibit this would damage our cells (This is why there are no antibiotics for viruses)

Antibiotics are chemicals designed to kill or damage prokaryotic cells

Fighting Infectious Disease

Diseases that can be fatal if not for Antibiotics

Acetobacter – cause pneumoniaAnthrax – fever, chills, chest discomfort, shortness of breath, confusion or dizziness, cough, nausea, vomiting, headache, sweats, and deathGonorrhea – STD, burning sensation when urinating, discharge from penis or vagina, vagina bleeding between menstruation, etc…….


Salmonella – diarrhea, fever, and abdominal cramps. Can lead to death. Tuberculosis – frequent cause of death worldwide. Bad cough, pain in the chest, coughing up blood, weakness, weight loss, no appetite, chills, fever.

There are many more examples


Passive Immunity• Antibodies produced against a pathogen by

other individuals or animals can be used to produce temporary immunity

• Usually last only a short time because the immune system eventually destroys foreign antibodies

• Can occur naturally:• Like from pregnant woman to fetus; across placenta

or breast milk

Immune System Disorders

A strong immune response to harmless antigens can produce allergies, asthma, and autoimmune disease

Allergies – when allergens enter the body and trigger an inflammatory response by causing most cells to release histamines• If it occurs in the respiratory system it increases

mucous production and causes; sneezing, watery eyes, a runny nose, etc

Antihistamines – a drug that helps response by reversing histamine reaction.


Asthma – a chronic disease in which air passages narrow, causing wheezing, coughing, and difficulty breathing• Can be both caused by heredity and/or

environmental factors


Autoimmune Disease• When the immune system attacks the body’s own

cells• Type I Diabetes – antibodies attack insulin-producing cells in the pancreas• Rheumatoid Arthritis – antibodies attack tissue around joints• Lupus – antibodies attack organs and tissues causing areas of chronic inflammation though out the body


LupisRheumatoid Arthritis


Opportunistic Disease – A disease that attacks a person with weakened immune system.AIDS – Acquired Immunodeficiency SyndromeHIV – the cause of AIDS; • Human Immunodeficiency virus

Immune System DisordersHIV is deadly for several reasons:

1. It can hide from the defenses of the immune system

2. Attacks key cells within the immune system1. Reduces the number of active lymphocytes2. A loss in the ability to produce antibodies

3. The virus mutates quickly

• HIV is a retrovirus• A Retrovirus carries its genetic material into the

cell


Transmission – only through infected blood, semen, vaginal secretions, or breast milk• Four Main ways HIV is transmitted:1. Sexual intercourse2. Sharing needles3. Contact with infected blood products4. From infected mother to her child during

pregnancy, birth, or breast feeding

Immune System DisordersCases of AIDS are not evenly distributed.

AIDSWhat are the reasons for uneven distribution?Is there a moral obligation?


Only no-risk behavior with HIV transmission is abstinence from sexual activity and IV drug useNo cure but a new variety of drugs makes it possible to survive

Make sure to read page 180 – 181 : Issues Related to AIDS

TOK

The different methods of transmission of HIV each carry their own risk.

How can individuals in different societies minimize or eliminate each of these risks?

causes: germ theory of disease led by louis pasteur (french) and robert koch (german) bacteriologist...

Documents