Immune System Pre-AP Biology Chapter 40-2. Immune System Overview Function: fight infection through the production of [specialized] cells that inactivate.

Immune SystemPre-AP BiologyChapter 40-2

Immune System Overview•Function: fight infection through the production

of [specialized] cells that inactivate foreign substances or cells

•It is main defense against pathogens▫Recognizes, attacks, destroys, and “remembers”

each type of pathogen that enters the body•2 general categories:

▫Nonspecific defenses (fortress walls of the body)▫Specific defenses (security guards of the body)

Nonspecific Defenses•First line of defense: skin

▫Most important nonspecific defense!▫Very few pathogens can penetrate the skin

Must have an opening – a cut, scratch, mouth, nose▫Mucus, saliva, and tears have lysozyme – enzyme

that breaks down bacteria’s cell wall▫Oil and sweat glands produce acidic

environment▫Mucus and cilia in nose and throat trap and push

pathogens away from lungs▫Acid and enzymes destroy bacteria that make it

to your stomach

Nonspecific Defenses•Second line of defense: inflammatory response

▫Reaction to tissue damage caused by injury/infection

▫When pathogens are detected: White blood cells flood area through blood vessels

near wound Many WBC are phagocytes – engulf and destroy

Releases chemicals that increase core body temperature (fever) Many pathogens only survive in narrow temp. range Increased temp also increases heart rate = more

WBC

Nonspecific Defense to Viruses

•Sometimes, virus-infected cells produce a group of proteins that help other cells resist infection: Interferons▫Named this because they “interfere” with

growth of the virus▫Slows the progress of infection and gives

specific defense system time to respond

Specific Defenses

•Called “immune response”•Triggered by antigens•2 types of lymphocytes

▫B lymphocytes (B cells) – work in body fluids Humoral immunity

▫T lymphocytes (T cells) – work in living cells Cell-mediated immunity

Humoral Immunity•B cells detect pathogen and multiply rapidly

▫Produces large numbers of plasma cells and memory B cells

•Plasma cells release antibodies (proteins that recognize and bind to antigens – recall blood types!)▫Antibodies carried in the blood stream to

attack•Memory B cells remain capable of

producing antibodies specific to that pathogen after exposure

Antibody Structure•Antibody is shaped like a “Y”

and has two identical antigen binding sites▫Differences in amino acids

affect shape of binding sites▫Shape of binding site is how

antibody recognizes antigen▫Healthy adult can produce

about 100 million different types of antibodies!

Cell-Mediated Immunity• Primary defense against own cells when

cancerous or infected• Also important for fighting fungi and protists• Process: T cells divide and differentiate

into…▫Killer T cells – destroy bacteria, fungi,

protozoan or foreign tissue with the antigen▫Helper T cells – produce memory T cells▫Suppressor T cells – shut down killer T cells

after pathogenic cells brought under control▫Memory T cells – cause response if same

antigen enters again

Transplants

•Killer T cells make organ transplants difficult▫Recognize new organ as foreign and attack it

Called “rejection”▫To prevent rejection, donor should have cell

markers nearly identical to recipient; and▫Recipient usually takes drugs for the rest of

their life to suppress cell-mediated immune response.

Acquired Immunity

•Remember Jenner’s smallpox??▫Cowpox infection to create immunity to

smallpox

•Can be active or passive

Active vs. Passive ImmunityActive Passive

• Type of immunity produced by reaction to a vaccine

• Vaccination: injection of weakened or mild form of pathogen

• Stimulate immune system to create plasma cells

• Plasma cells are ready to make specific antibodies

• Appears AFTER exposure• Can be natural or deliberate

• Antibodies produced by other animals injected into the bloodstream

• Lasts for short time – body eventually destroys them

• Can be natural or deliberate

• Natural: from mother to fetus or in breastmilk

• Deliberate: vaccine▫ Tropical diseases ▫ Rabies