How do your cells fight off invaders? Immune response How do your cells fight off invaders?

Introduction You do not get sick every time disease causing germs enter your body. Sometimes white blood cells attack and destroy invaders without your feeling ill. Other times, you get sick because germs start winning. Fortunately, a healthy immune system can overpower many different types of germs – even when germs temporarily gain the upper hand.

Pathogen A disease causing agent Types of Pathogens: Bacteria Viruses Others: Fungi (athlete’s foot), Protists (Malaria) & Parasites (heart worm) They cause disease by destroying cells, releasing toxins and/or disrupting body functions

How do pathogens enter the body? Direct Contact Requires an infected person or animal to have physical contact (blood/bodily fluids) with a healthy person (Ex. Rabies or HIV) Indirect Contact Pathogens surviving on non-living surfaces (tables, door knobs, etc.) Air – coughing & sneezing Vectors Anything that carries a pathogen & transmits it to healthy cells (mosquitoes)

Draw the Following in your notes:   Bacteria Virus Size (Compared to each other) Shape Living or Non-living # of Cells Reproduction DNA & RNA? Treatment Can it be beneficial? Examples

(compared to each other)   Bacteria Virus Size (compared to each other) Huge compared to viruses Sub-microscopic particles (tiny compared to bacteria) Shape Spheres, rods or spiral Microscopic particle Living or Non-living Living Non-living (although it’s debated – they do not meet all of the criteria of living things) # of Cells Unicellular None – not living Reproduction Fission – a form of asexual reproduction Cannot reproduce on their own. They replicate by infecting a host cell.

Bacteria Virus How is it treated? Can it be beneficial? Examples   Bacteria Virus DNA & RNA?   Yes DNA or RNA (enclosed in a protein coat). Can mutate & evolve. How is it treated? Antibiotics “Let nature take its course” Vaccines are preventative Can it be beneficial? Yes (used to make cheese & yogurt!) No Examples Strep throat, E.Coli, food poisoning Flu, colds, AIDS

How do we control Pathogens?

Antibiotics Medicines that target bacteria & fungi and keep them from growing & reproducing Can ONLY be used for bacterial and fungal infections!!! Antibiotic resistance occurs when bacteria mutate so they are no longer affected by antibiotics

Vaccines A killed or weakened form of a pathogen that is injected into your body which causes it to build an immunity to that type of virus

What is the Function of the immune system? To fight off infection & pathogens Antigen – any substance that causes your body to produce antibodies (proteins) against the invader Antigens trigger a response by your immune system Pathogens can also be antigens Two lines of defense…

Non-specific Defenses *They react the same to all pathogens Also called passive defenses Skin – forms a barrier that few pathogens can get through Inflammation – swelling Mucus, saliva & tears – trap pathogens and contain enzymes that kill bacteria Fever – higher body temp slows the growth of many pathogens

Specific Defenses *Different for every pathogen Also called active defenses White blood cells (B cells & T cells) Travel through the blood stream & attack pathogens Example: Phagocyte (type of white blood cell that destroys pathogens by surrounding and engulfing them)

Specific defenses cont’d Antibodies (proteins) Some cause pathogens to clump making them easier to engulf Some track down and destroy infected cells Some called memory cells, will remain in the body so if that pathogen appears again, they will quickly respond