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

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

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

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)

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

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

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

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