1. Immune System

2. Infection and Immunity
Skin (integumentary system) is first line of nonspecific defense in protecting body against any foreign invader (pathogen) that can cause infection (usually viruses or bacteria) since it provides a barrier
Break in skin barrier allows pathogen to enter & infect
Second line of nonspecific defense is phagocytosis (white blood cells that eat invader)

3. If phagocytes cannot prevent pathogen from infecting, body undergoes specific defense in which it identifies and targets specific pathogen
Pathogen is now considered an antigen since it causes immune response (usually a virus)
Body produces specific Y-shaped proteins called immunoglobulins (Ig) or antibodies (ANTI-body) to kill antigen (ANTIbody GENerator) using lock & key mechanism (antigen = key, antibody = lock)

4. Antibody is produced when helper T-cell (from Thymus) causes B-cells (from Bone) to construct specific antibody
Antibodies bind to antigen, now phagocytes can eat and destroy them
Entire process takes 7-10 days
Some B cells turn into Memory B cells that will always be prepared to immediately kill same antigen so that individual never experiences symptoms

6. Vaccines
A vaccine is an injection of weakened or dead antigen into the body
The immune response produces antibodies as body can’t tell it’s harmless.
Antibodies with phagocytes destroy antigens
Memory-B cells permanently remember antigen so if body encounters it again, immediate attack occurs before disease symptoms develop making individual immune from disease

7. Bacteria & Viruses
A microbe is anything too small to be visible to the naked eye. Two types of microbes are bacteria and viruses.
Bacteria are single-celled prokaryotic living organisms
Viruses may have a spiny outside layer, called the envelope. Viruses have a core of genetic material (DNA or RNA), but cannot reproduce on their own. They infect cells and take over their reproductive machinery to reproduce. They are not considered living.

8. Bacterial infections can be treated with the non- specific immune response or antibiotics, medicines that destroy prokaryotic bacteria without harming eukaryotic humans
Viruses cannot be treated with any medicines, solely the immune response

9. Compromised Immunity
If the immune system is compromised or not working, individual may not be able to survive simple infections like flus or pneumonia
In AIDS (Acquired Immune Deficiency Syndrome), T-helper cells are infected by HIV (Human Immunodeficiency Virus), thus weakening immune system
AIDS patient usually dies from pneumonia