The Immune System

The Different Types of Pathogens

These pathogens may be spread in many different ways:

1)Human to Human in Direct or Indirect contact

2) Contact with a contaminated environment: Either through the air, water, or food

3) Contact with contaminated materials (can be part of indirect contact, like drinking from the same mug as a sick person)

4) Infection by animal contact (like flies or roaches) or animal bites (like rabies from a dog, or Malaria from a fly, or Lyme's disease from a tick)

Lucky for us, our bodies are very good at keeping these pathogens out!

We have 3 main lines of defense to keep pathogens from making us sick!

1) The Barriers to entry: these are like skin, tears, mucus, and stomach acid. These keep pathogens from getting inside the body where they can infect and cause damage.

2) The inflammatory response (Innate Immunity): This is non-specific and will attack everything in your body the same way. Phagocytes, a white blood cell (WBC) will seek and engulf whatever is foreign to your body.

3) The Immune Response (Adaptive Immunity): This is highly specific to the type of antigen you are infected by. An antigen is a molecule on a pathogen that may be recognized as foreign to your body's defenses. These antigens are like a team uniform. Here, cells called lymphocytes, to produce antibodies to seek, mark, and destroy pathogens. T-cells recognize and tell the body something foreign is present. B-cells "bang bang" or produce the antibodies which kill the targeted pathogens.

Active Vs. Passive Immunity

Active Immunity: when a person has encountered a specific antigen and can produce the antibodies for that pathogen. Because they know how to produce the antibodies, a person with active immunity is immune for a very long period of time -- sometimes for life.

Vaccine: a vaccine is when weakened or killed versions of the pathogen are introduced to the body. These pose no threat to the individual, but stimulate active immunity, protecting the person from the real pathogen.

Passive Immunity: Only antibodies are given to a person (like a mother passing her immune system on to a child). Because they have never encountered the disease, they are unable to produce more antibodies. This immunity only lasts for a short time.

Allergies:

Allergies occur when an individual is overly sensitive to allergens (like pollen or cat hair) that pose no threat to health. The body responds by releasing histamines. Histamines are chemicals that cause the symptoms of an allergy, which is why we use anti-histamines in drugs like Benadryl to treat allergy attacks.

Antibiotics:

Antibiotics are drugs that are used to treat bacterial infections only. Antibiotics interfere with the way bacteria grow and multiply.