First Line of Defense Skin Sweat Tears Saliva Stomach Acid Nose Hairs & Mucous

What if the first line of defense lets a pathogen by?? A macrophage (above with streptococcus), begins the second line of defense. A macrophage recognizes a pathogen by its marker proteins The macrophages surrounds and eats the pathogens. Then it places a piece of it on its outer membrane (a victory banner) Second Line of Defense A macrophage is the biggest white blood cell in the body

The T-cells communicate two things 1.Tell B-cells to make antibodies 2.Tell Killer T-cells begin dividing. 3 rd Line of Defense Helper-T Cells are the cheerleaders for the immune system Become activated by macrophages

B cells produce antibodies that circulate in the blood and lymph streams

Antibodies are made to mark only a certain kind of pathogen. Antibodies recognize foreign antigens and mark them for destruction by macrophages and killer T- cells

Killer T-cells look for infected cells and kill them. (The Killer T- cell is marked by the arrow. It is killing a much larger influenza virus infected target) They will also kill any pathogens that have antibodies surrounding them These killer T-cells recognize and kill the same pathogens that the macrophage killed earlier.

The Suppressor T-cell tells the B-cells when the body can stop making antibodies.

T-cells & B-cells leave behind memory cells that watch for the pathogen. If they find one, they start multiplying to kill it. This process is so immediate & explosive that the pathogen is killed before you know you are sick. You are immune to that pathogen

First Introduction Second Introduction Time

Allergies – an abnormal response to a pathogen (pollen, dust, pets etc.) Immune system is super-sensitive to the pathogen and initiates the first line of defense.

Viruses are made up of a protein coat and RNA or DNA It is debated whether viruses are living or non-living things since they cannot reproduce on their own. Viruses inject their DNA/RNA into our cells and our cells produce the viruses. After the cell produces the viruses the cell dies. To combat a virus we use vaccines. Vaccines help our body to produce memory cells

Some viruses like HIV are called retro viruses they contain RNA instead of DNA

Bacteria can help us do many good things: make yogurt, treat water, clean oil spills etc. Bacteria are living things (Monera) Antibiotics kill bacteria by damaging their cell wall This doesn’t affect our cells because they do not have cell walls