o
Robert Koch- “father of disease”
o research focused on anthrax
o Koch’s Postulates

Initial reaction of body to ALL pathogens
 Pathogen-any agent that causes disease
▪ Ex: bacteria, virus, fungi, parasites

Come into contact with the body by:
 Air
 Food
 Water
 Person-to-person contact
 Animal bites
 Skin – prevents entry
 Oil – traps and kills invaders
 Sweat-have toxins that can kill bacteria
 Mucous Membranes – epithelial tissue that protect the interior
surfaces of the body.
▪ Mucous-sticky fluid that traps pathogens
 Hair/Cilia
▪ Respiratory tract into digestive tract
 Tears
 Saliva
 Ear wax
If a pathogen penetrates the first line of defense...
Inflammatory Response: series of reactions that suppress infection and speed
up recovery.
1. Cells are damaged. Ex: cut, pathogen invasion
2. Damaged cells release histamine
o Causes increased blood flow and permeability of blood vessels around
injured area
o Histamine causes redness, swelling, warmth, pain
o Sends signal to white blood cells to come
3. White blood cells (Phagocytes) arrive
o Phagocytes ingest and destroy pathogens
o 2 Types of Phagocytes: Neutrophils & Macrophages
4. Platelets arrive-seal off surrounding tissues and stop pathogens from
entering the rest of the body

Natural Killer Cells-large white blood cells that attack pathogeninfected cells
 Can kill cancer cells and virus-infected cells
 Pierces cell membrane to kill the cell

Fever
 Increase in body temperature
 Slows growth of bacteria and viruses
 Promotes WBC activity

Complement System
 Proteins circulate in blood and become active when they encounter
certain pathogens
 Some puncture infected cell membranes to kill the cell

Interferon
 Protein released by virus-infected cells
 Causes nearby cells to make proteins that help them resist the virus
infection
When pathogens get past the NonSpecific Defense…
Aimed at SPECIFIC pathogens
o
Immune System-cells and tissues that recognize and attack foreign substances
o Tissues:
o Bone marrow-makes lymphocytes
o Thymus-gland where T cells mature
o Lymph nodes-contain lymphocytes, filter lymph
o Spleen-stores healthy blood cells, breaks down old blood cells, helps develop
lymphocytes and other WBC, collects pathogens
o Tonsils & Adenoids- masses of lymph tissue found in nose and throat that
contain lymphocytes which produce antibodies
o Cells:
o Lymphocytes (WBC of the immune system)
o 2 Types:
o B Cells-made in bone marrow and mature there
o T Cells-made in bone marrow, but mature in thymus

Lymphocytes react to presence of antigens
 Antigens-proteins on the surface of pathogens
Lymphocytes have unique receptors on surface
that match specific antigens
 Matching lymphocytes bind to antigen to start
attack
 Immune Response-reaction of the body against
pathogens


An immune response begins with:
 1) Macrophage engulfs a pathogen
 2) Macrophage displays fragments of the
pathogen’s antigens on its surface
 3) Helper T cell (lymphocyte) with matching
receptors to the antigens binds to the macrophage
 4) Macrophage releases proteins that activate
more helper T cells


The immune response occurs in 2 parts,
which happen simultaneously
Part 1- Cell-Mediated Immune Response
 Increase in Helper T cells and their division rates
 Cytotoxic T cells are produced
▪ Recognize and destroy pathogen-infected cells
▪ Cytotoxic T cells have receptors that match antigens
▪ Puncture the cell membrane to kill it

Part 2- Humoral Immune Response
 B cells that have matching receptors to the antigen
divide
 Change into plasma cells and memory cells
▪ Plasma cells-make antibodies
 Antibodies-defensive proteins that are released into blood
▪ Antibodies bind to specific antigen
▪ They do not destroy the pathogens directly
o
Some B cells turn into memory cells
o Lymphocytes that will not respond the 1st time they meet an
antigen, but will recognize and attack with later infections
o Explains why you get most diseases only once
o
Primary Immune Response
o First time the body encounters an antigen
o Memory cells produced for that specific antigen
o
Secondary Immune Response
o Later infection by the same pathogen
o Memory cells respond faster and stronger
o
Exception: Cold and Flu viruses

Immunity-the ability to resist an infectious
disease
 Memory cells
 Vaccinations

Vaccine-solution that contains a dead or
weakened pathogen
 Body produces primary immune response
▪ Memory cells
 Booster shots

Can react to harmless antigens in
ways that can be harmful
 Allergies, Asthma, Autoimmune
Diseases

Allergy-a physical response to an
antigen
 Many symptoms due to histamine
▪ Antihistamines-drugs that counteract
effects of histamines and relieve symptoms
of allergies

Allergies can trigger Asthma
 Respiratory disorder
▪ Bronchioles narrow
▪ Swelling and inflammation
▪ Difficulty breathing

Autoimmune Diseases
 Disease where the immune system attacks the organism’s
own cells
 Ex: Multiple sclerosis
▪ Nervous system
▪ T cells attack insulating material in nerve cells in the brain, spinal
cord, and nerves in eye
▪ Cause weakness, tingling, blurred vision
 Severe cases can cause paralysis, blindness, death

AIDS- Acquired Immunodeficiency Syndrome
 The immune system loses its ability to fight off pathogens and
cancers

AIDS results from infection by HIV
 HIV-Human Immunodeficiency Virus
▪ Destroys Helper T cellscripples the immune systemleads to AIDS

Opportunistic Infections-illnesses caused by pathogens that
produce disease in people with weakened immune systems
 Usually these pathogens don’t create problems in healthy people

HIV does NOT cause death, but AIDS is fatal
 Death caused by weakened immune system’s inability to fight
opportunistic infections and cancers

HIV is transmitted by body fluids and contaminated needles
*PLAY DISCOVERYEDUCATION VIDEO*
Type of Cell
Function
Macrophage
Neutrophil
Engulfs and kills pathogens
Helps initiate immune response
Engulfs and kills pathogens
Natural Killer Cell
Punctures infected cells
Helper T Cell
Cytotoxic T Cell
Activates cytotoxic T cells
Helps B cells multiply to form antibodies
Puncture labeled infected cells
B Cell
Labels invaders for destruction by macrophage
Plasma Cell
Releases antibodies
Memory Cell
Stores information about a pathogen