Infectious Disease and the Immune System

Ch. 39

What are Infectious Diseases?• Pathogen- bacteria, virus,

fungi, protozoa, etc…– Any organism that disrupts

homeostasis• Infectious Disease- change in

homeostasis by a pathogen– Foreign pathogen– Symbiotic pathogen that has

changed location– Body is too weak for symbiotic

relationship

Types of Diseases?• Infections diseases Pathogens• Genetic disease gene mutations– Trisomy 21 (Down’s Syndrome)

• Environmental toxin exposure– Cirrhosis

• Malnutrition limited food supply– Scurvy

• Cancer Carcinogens– Lung Cancer– Brain tumor

• Diabetes Genetics/Malnutrition

Identifying a New Disease• Robert Koch; 1876

– Isolated anthrax from dead animals and injected into healthy ones

– Healthy animals died of disease– Isolate pathogen in new dead

animals and found it to be the same anthrax

• Koch’s Postulates:1) Same pathogen must be found in

the host in every case2) Pathogen must be grown on a

culture plate3) Once grown, the pathogen must

give a healthy organism the disease

4) Pathogen in the new host and the old host must be the same

Spreading Disease• 4 methods:1) Direct Contact

-colds, STDs, FluCarriers- transmit disease but are not effected by itIncubation period- time it takes after infection for symptoms to appear2) By Object

-food poisoning 3) Airborne transmission

-Strep throat 4) Vectors

-insects, birds, farm animals-Malaria; mosquitoes -Black Plague; fleas on rats

Disease Patterns• Endemic Disease:

always present in the population; cases fluctuate with seasons

ex. Cold, flus, food poisoning• Epidemic Disease:

small population see dramatic increase in a new or uncommon disease

ex. SARS• Pandemic Disease:

global spread of diseaseex. HIV/AIDS; H1N1

Pathogen Attack!• Pathogens damage host cells

through toxinsproteins/compounds that:

-inhibit cellular functions-destroy the plasma

membrane-produce fever-inhibit cell signaling

Botulin neurotoxin-most powerful discovered

so far; 75 ng can kill a human-prevents neurotransmitter release-causes muscle paralysis-used to make BOTOX

The Immune System• Immune system- various

methods of defending, isolating, and removing pathogens from the body

• Innate Immunity– Nonspecific defenses against

all pathogens• Acquired Immunity– Defense against specific

pathogens that is built over time

– Made from Antibody immunity and Cellular immunity

Innate Immunity• Levels of defense:1) Skin- protective barrier covering the body2) Secretions- mucus, oil, sweat, tears, and any other fluid used to wash away pathogens– Also contain lysozyme enzyme

3) Inflammation- increase blood flow and temperature of infected area to kill pathogens– Caused by Histamine, AA

hormone released by Basophils and Eosinophils (white blood cells)

Innate Immunity4) Phagocytes- white blood cells that kill pathogens with phagocytosis

– Endocytosis of bacteria

Types of Phagocytes:1) Macrophages- white blood cell

in tissue2) Neutrophil- second wave if

macrophages are not enough3) Monocytes- travel in the blood

to infection site and become macrophages

Over time infections produce pus (collection of living and dead macrophages)

Innate Immunity5) Interferons- protective proteins that cover cells so viruses cannot attach to host cells– Specific for different types

of host cells– Also produce antiviral

proteins to stop virus reproduction

Macrophages from the innate immune system are used to build the acquired immune system

Acquired Immunity• ID system through antigens

and antibodies• Antigens- proteins in the cell

membrane used in cellular communication– A-type Blood A-type antigens– Bacterial membrane antigens

signal attachment mechanism• Antibodies- proteins in the

blood produced to attach to specific antigens– If the antibody finds the antigen

is was made for; that organism attached to those antigens is destroyed

Lymphatic System• System for monitoring tissue fluid and

filter body fluids for infection• Lymph- tissue fluid inside lymph vessels

– Travels through capillaries and veins on the Lymph system

– Return tissue fluid to blood in the shoulders

• Lymph nodes- mass of tissue for filtering lymph with lymphocytes (white blood cells)

• Tonsils- filter out pathogens we breath in• Spleen/Thymus Gland- store lymphocytes• Lymphocytes react with pathogens to

build antibodies– Create Antibody and Cellular Immunity

Antibody Immunity1) Infection occurs and

macrophages eat pathogens2) Antigens from pathogens

are placed on the macrophage membrane

3) Lymphocytes (Helper-T cells and B cells) bind to antigens and create plasma cells

4) Plasma cells produce 2000 antibodies/sec to kill infection

5) Memory-B cells and antibodies stay in blood to stop infection quickly if it returns

Cellular Immunity1) Infection occurs and macrophage

eats pathogens2) Antigens from pathogens are

placed on the macrophage membrane

3) Cytotoxic (Killer) T cells activate and release perforin on to pathogens

4) Perforin eats through membranes, killing the pathogens

Over active reaction can lead to autoimmune disorders

-body tissue is attacked-transplanted organs are

attacked

Passive vs. Active ImmunityPassive:

Natural-Antibodies pasted down from

mother/breast milk

Artificial-Take antibodies from organism already immune from disease

Active:Vaccine-Inject person with weak or dead pathogen; body easily kills it and makes antibodies

Cowpox is a vaccine for Smallpox

Homework: HIV/AIDS paper• Write a 1 page essay on HIV:– How it spreads?– How does it effect the immune

system?– What is AIDS?– What are methods of

controlling the spread of HIV?– Are there ways to cure HIV?

A lot of content so be brief in your explanations