1. Animal defense Castle analogy
Walls and moats – don’t allow microbes in
Skin – first line of defense
Roaming patrols – if something does get in, mount a cellular attack – use a bunch of cells and chemicals to kill microbe – happens very rapidly after onset of infection
Innate immune system (Non-specific) - second line of defense
Security guards – check every cell they encounter to see if its foreign or not
Adaptive immune system (specific) – third line of defense

2. Skin (walls and moats) Two layers Functions Epidermis Dermis
Cells are continuously being worn away and replaced from cells from the basal layer (layer that forms boundary between epidermis and dermis)
Dermis
Contains nerve endings, sweat glands, hair follicles
Much thicker than epidermis
Subcutaneous layer (fat cells called ???) is found underneath the dermis
Functions
Prevents microbes from entering the body
Oil glands and sweat glands release chemicals that makes the surface acidic
Sweat also contains lysozyme, an enzyme that kills many bacteria by destroying cell walls
In addition to the skin, other surfaces help in defense:
Saliva contains lysozyme
Stomach is acidic to help kill microbes
Sticky mucus lines the naval cavity and lungs
Cells with cilia sweep mucus up the respiratory tract so that it can be swallowed and killed

3. Innate immune system 4 types of defenses Cellular attack
When something foreign enters, white blood cells of the innate immune system attack no matter what type of cell (non-specific)
3 types
Macrophages – how do they kill cells?
Neutrophils – how do they kills cells?
Natural Killer cells
They kill our own cells that have already been infected
Release a protein called perforin
This forms a hole in the membrane
Complement system
Free floating proteins in the plasma
Can only insert themselves into cell walls (so bacteria and fungi only)
Forms a hole in the cell wall
Temperature response
Macrophages send a signal to the brain to raise the temperature
Called a fever – inhibits microbial growth
Too much heat though can destroy normal proteins – by what process?
Inflammatory response
Damaged cells release chemicals
Histamine
These chemicals cause blood vessels to expand
Increases blood flow to the injury
This stretches the walls of the capillaries
Why there is often swelling and redness with infection
Stretched walls allows neutrophils and macrophages into the site of the infection
They engulf pathogens and remains of dead cells
Leads to the formation of pus

4. Adaptive Immune system
When something foreign enters the body, white blood cells of the adaptive immune system attack only the foreign substance that entered (specific)
Involves T lymphocytes and B lymphocytes
T lymphocytes migrate to the thymus after being made in bone marrow
4 types
Helper T cells
Memory T cells
Cytotoxic T cells
Suppressor T cells
T cells recognize antigens and then attack (discussed later)
Antigens are foreign molecules that evoke an immune response
B lymphocytes remain in the bone marrow until needed
B cells also recognize antigens and then attack by making antibodies (discussed later)

5. T lymphocytes – cellular response
Macrophage engulfs foreign body with antigen
Processes the antigen and transports it to the plasma membrane
Macrophage releases interleukin-1, which recruits helper T cells
Helper T cell binds to antigen and releases interleukin-2, which signals cytotoxic T cells to divide and make more copies
Cytotoxic T cells find cells with antigens and kill them similarly to natural killer cells (how?)
Some cytotoxic T cells become memory cells, which can recognize the antigen if it is seen later and mount the same response but only faster this time

6. B cells – the humoral response
B cell recognize either free-floating antigens or antigens from helper T cells
Helper T cells help B cells divide
B cell divides into 2 types of cells
Plasma cells – short lived, make lots of antibody
Memory cells – same as before, help with later attacks
Antibodies bind to invading microbes and signal to macrophages and natural killer cells to destroy them

7. Vaccinations
Vaccination is the process by which a disabled pathogen (microbe) is introduced into the body
Antigens on the disabled pathogen initiate an immune response, which generates memory cells
Later, if exposed to the actual microbe, memory cells will be ready to respond much more quickly

8. HIV and AIDS HIV is an disease that affects the immune system
HIV infects helper T cells
Helper T cells are needed for which immune response?
Cellular?
Or Humoral?
HIV progresses to AIDS when the number of helper T cells drops below a certain number (there is no adaptive immune system essentially)
AIDS patients can then succumb to a number of diseases
Your books states that no one has survived once diagnosed with AIDS – not true