The Immune The Immune SystemSystem

Chapter 43Chapter 43

The Immune System An animal must defend itself against:

Viruses, bacteria, pathogens, microbes, abnormal body cells, toxins, and other foreign substances

Innate immunity is present at birth

Acquired immunity develops after exposure to foreign substances

Innate Immunity External defenses/Non-Specific include skin,

mucous membranes, and antimicrobial proteins like lysozyme, an enzyme that digests the cell walls of bacteria.

Phagocytic Cells attach to invaders and eat them, they include: Neutrophils: the most abundant white blood cell Macrophages: “big eaters” Eosinophils: attack parasites Dendritic Cells: ingest microbes

Innate Immunity Interferons are proteins

that protect against viruses

An inflammatory response is triggers when tissue is damaged

Mast cells in tissue release histamines which increase blood flow to the injured site

Innate Immunity Natural Killer Cells patrol the body and attack

virus-infected body cells and cancer cells.

Acquired Immunity An antigen is a foreign molecule that triggers

an immune response

Binding sites on antigens are called epitopes, this is where antibodies attach. They fight the invaders.

Lymphocytes Lymphocytes are white blood cells. They are

found in our blood, and fight antigens. They are made in our bone marrow.

B cells B cells are a type of lymphocyte that mature

into plasma cells that produce antibodies. Antibodies are specific towards a particular antigen and mark it for destruction.

B cells make up our humoral immune response

T cells T cells can bind with fragments of antigens.

They bind to surface proteins.

They make up the cell-mediated immune response and destroy invaders.

Types of T cells Some T cells have the CD4 protein on them,

and they are called “helper T cells”

Other T cells have the CD8 protein on them, and they are called cytotoxic or “killer T cells”

Types of Antibodies Antibodies are shaped like the letter Y and

bind to antigens. There are 5 classes:

IgM

IgG

IgA

IgE

IgD

IgM IgM respond first to antigen exposure, and

attempt to neutralize them.

IgG IgG: Most abundant antibody in the blood,

crosses placenta to give passive immunity to fetuses.

IgA IgA: present in tears, saliva, breast milk, and

mucus

IgE IgE: triggers release of histamines in

response to allergic reactions

IgD IgD: present on B cells, binds to antigens,

stimulates B cell production

Active vs. Passive Active immunity develops after exposure to

an infectious agent, or through immunization or vaccination.

Passive immunity is when antibodies from one person are transferred to another, uninfected, person (usually mom to fetus)

Allergies Allergies are exaggerated (hypersensitive)

responses to certain antigens called allergens.

An acute allergy is called anaphylactic shock which can cause breathing problems and possibly death.