The Immune System

The Body’s Defense

The Body’s Lines of Defense

The body has three lines of defense against pathogens:1. Barriers - skin, breathing passages, mouth, and

stomach trap and kill most pathogens.2. Inflammatory Response - fluid and some WBC’s

leak from blood vessels into tissues to fight pathogens.

The WBC’s are called phagocytes- they engulf and destroy the pathogens.

Inflammatory responses include a red, swollen, warm area and sometimes fever.

3. Immune Response- these cells can distinguish between different kinds of pathogens and react to each kind with a specific defense.

LymphocytesWBC’s that target specific pathogens are called

lymphocytes.2 major types:

1. T Cells- identify pathogens by recognizing their antigens.

Antigens are molecules that the immune system recognizes as either a part of your body or coming from outside your body.

2. B Cells- produce chemicals called antibodies. Antibodies bind to antigens and destroy them. Each kind of B Cell produces an antibody that

can only bind to one kind of antigen.

Non-Infectious DiseasesNon-Infectious diseases are NOT caused by micro-

organisms and are NOT spread from person to person.1. Allergy- the immune system is overly sensitive to a

foreign substance- something not normally found in the body.

Allergen- any substance that causes an allergy: dust, pollen, molds, some foods or medicines.

Histamine- chemical responsible for symptoms of allergies, like sneezing or watery eyes.

Asthma- when the respiratory passages narrow causing the person to wheeze and become short of breath.

Non-Infectious Diseases2. Diabetes- when either your pancreas fails to produce enough insulin or your body’s cells cannot use it properly. As a result, there are high levels of glucose in the blood and glucose is excreted in the urine. The body cells do not contain enough glucose.

Insulin - produced by pancreas- chemical that enables your cells to take in glucose from the blood and use it for energy.

Type I Diabetes- most serious- person needs insulin injections.

Type II Diabetes - controlled by diet, weight control, and exercise.

Non-Infectious Diseases3. Cancer - a disease in which cells multiply uncontrollably, over and over, destroying healthy tissue in the process.

Tumors develop when a cancerous cell divides over and over to form abnormal tissue masses.

Surgery, drugs, and radiation are used to treat cancer.

Carcinogens are substances or factors in the environment that can cause cancer. Avoid carcinogens such as tobacco or over-exposure to sunlight.

Infectious DiseasesInfectious diseases are disease that can pass

from one organism to another.

Pathogens are organisms that cause disease. Diseases caused by pathogens are infectious.

The four major groups of human pathogens are:1. Bacteria2. Viruses3. Fungi4. Protists

Infectious DiseasesBacteria- one-celled microorganisms

Examples include strep throat and tetanus.Other bacterial pathogens produce a poison

called a toxin that damages cells.

Viruses- smallest pathogensCannot reproduce unless inside living cells.When viruses infect cells, the cells are

damaged or destroyed, and the damaged cells release new viruses to infect other cells.

Examples include influenza (flu), colds, chicken pox, and AIDS.

Infectious DiseasesFungi- example- athlete’s foot

Protist- example- malaria

Sources of pathogens include: Another person - physical contact like shaking hands,

or indirect contact like sneezing or coughing.Contaminated object - eating food, drinking water, or

using silverware that’s infected.Animal BiteEnvironment - tetanus and botulism live naturally in

the environment.

Preventing Infectious Disease

Immunity- the body’s ability to destroy pathogens before they can cause disease

Two types of immunity:1. Active- antibodies come from the person2. Passive- antibodies come from outside the

person

Preventing Infectious Disease

1. Active Immunity -occurs when a person’s own immune system produces antibodies in response to the presence of a pathogen.

T Cells and B Cells help destroy pathogens and keep a “memory” of the pathogen’s antigen.

Lasts for many years and sometimes for life. Ex: chicken pox.

Vaccination - (immunization)- harmless antigens are deliberately introduced to a person’s body to produce active immunity.

Vaccine - the substance used in vaccinations. Consists of pathogens that have been weakened or killed.

Preventing Infectious Disease

2. Passive Immunity - when the antibodies that fight the pathogen come from another source rather than the person’s own bodyLasts no more than a few months.Babies acquire passive immunity to some

diseases before birth from their mother.You develop immunity from some diseases

because you have had them before or you have been vaccinated. You will still become sick from them from time to time.

Antibiotics - chemicals that kill or slow down the growth of bacteria. No medications cure viral illnesses!!