31.2 Immune System

KEY CONCEPTThe immune system is a body system that fights infection and prevents illness.

31.2 Immune System

Many body systems protect you from pathogens.

• Many other tissues and systems help the immune system.– Skin: Physically block pathogens from entering the

body. – Mucous membranes: Found in the nose and throat;

Traps particles before they enter. – The circulatory system: Transports cells of the immune

system.

31.2 Immune System

Cells and proteins fight the body’s infections.

• White blood cells attack infections inside the body.– Phagocytes: Cell that engulfs and destroys pathogens. – T cells: Destroys infected body cells. – B cells: Produces antibodies.

31.2 Immune System

• Three types of proteins fight off invading pathogens.– Complement proteins weaken pathogen membranes.– Antibodies: Protein that causes pathogens to clump or

become ineffective. – Interferon: Proteins that stop viruses from reproducing.

antibody

pathogens

31.2 Immune System

Immunity prevents a person from getting sick from a pathogen.

• In all immunity, pathogens are destroyed before you get sick.

• Passive immunity occurs withoutan immune response.

Passed through:– mother’s milk– genetics

• Active immunity is gained after

the body undergoes a specific

immune response.

31.2 Immune System

BOTH

• Prevent future illness if the body becomes infected!

• Lytic Infection is an infection pathway in which the host cell bursts, releasing the new viral offspring into the host’s system, where each then infects another cell.

• In a Lysogenic infection, a phage combines its DNA into the hosts cell’s DNA.