ATI TEAS IMMUNE SYSTEM

What does the immune system do?

Protects the body from disease-causing agents known as pathogens.

What is the immune system composed of?

Innate defense and adaptive defense systems

Innate defense

A nonspecific response to pathogens by the immune system

Adaptive defense

A specific response by the immune system to a given pathogen

Innate immune system

A collection on nonspecific barriers and cellular responses that serve as an inborn first and second line of defense against pathogens.

What are the three (3) lines of defense of the innate immune system?

• The first (skin, mucus, secretions) keeps pathogens from entering the body

• The second (phagocytes, specific proteins, inflammatory response) fights pathogens that have entered the body

• The third is the adaptive immune system

Adaptive immune system

A kind of passive or active immunity in which antibodies to a particular antigen are present in the body.

What do lymphocytes such as B cells and various types of T cells do regarding pathogens?

They not only fight the pathogen but also retain a memory of the specific pathogen.

B cells

Lymphocytes that mature in bone marrow and make antibodies in response to antigens.

T cells

White blood cells that mature in the thymus and participate in an immune response.

How does the immune system prevents the entry of pathogens?

Through the presence of barriers (much like walls and moats) composed of the skin and secretions such as acid, enzymes, and salt.

What happens if the external barriers are breached?

There are cells and chemicals that act as soldiers to attack the pathogens.

What happens if the cells and chemical barriers fail?

The adaptive immune system specifically identifies, targets, and remembers the pathogen.

How can the immune system be visualized?

As layers of protection that include barriers to prevent entry, signaling, and targeting.

What is the ultimate function of the immune system?

To protect the body from a pathogen attack while allowing harmless molecules to enter the body.

How can pathogens enter the body?

Since the immune system functions through interactions with several other systems, pathogens enter through body openings of the digestive, urinary, and reproductive systems.

Injuries can also create ways for pathogens to enter.

Why is the lymph system critical to the functioning of the immune system?

Because pathogens from the blood also circulate through the lymph.

• B and T cells reside in the lymph nodes and are activated when a pathogen is encountered.

What are the nonspecific barriers of the innate immune system and what do they do?

Physical, cellular, and soluble components that impede pathogens from entering the body or multiplying.

What are the external barriers of the innate immune system?

The physical barrier of the skin and mucus secretions

What are the chemical barriers of the innate immune system?

Low pH, salt, enzymes

What are the cellular barriers of the innate immune system?

Commensal microorganisms

Commensal microorganisms

Microscopic organisms that live in or on the human body without causing it harm.

What happens if the pathogen breaches the barriers and enters the blood or tissues?

A second line of defense is activated.

• Ex: when a pathogen makes it into the body through a skin cut, mechanisms will go into effect to prevent the pathogens from affecting your body.

• One of the first responses is inflammatory response

What happens in an inflammatory response?

Histamines are released, increasing not only blood flow to the area but also the number of white blood cells known as phagocytes to the area.

• These phagocytes destroy bacteria.

What is released if a virus enters the body?

Interferons, which are proteins that interfere with the production of new viruses

What else is sometimes used by the body to speed up the immune response?

Fever

What are other internal barriers?

Antimicrobial peptides and “natural killer” (NK) lymphocyte cells that attack host cells that harbor intracellular pathogens.

Histamine

A white blood cell secretion that triggers capillary permeability and vasodilatation.

Interferons

Proteins secreted by leukocytes when they are infected with viruses.

Antimicrobial

A substance that kills or inhibits growth of microorganisms with minimal damage to the host.

What are the two (2) general responses the adaptive immune system has?

Cellular or humoral

What does a cellular response do?

Destroys the infected cell

What does a humoral response do?

Destroys pathogens found in body fluids using antibodies secreted by B cells.

How the adaptive immune system respond?

By remembering signature molecules, called antigens, from pathogens to which the body has previously been exposed.

Antigens

Substances on the surfaces of agents that act to identify them, to the body, as being native or foreign.

What are the functional cells of the adaptive immune system?

Lymphocytes called T and B cells

Antigen-presenting cell

A cell that displays foreign antigens with major histocompatibility complexes on their surfaces.

What do antigen-presenting cells (APCs) such as macrophages do?

Digest pathogens and present the pathogen’s antigen signature to “helper” T cells.

What happens depending on the type of antigen presented to the helper T cell?

Either a B cell or a cytotoxic T cell is activated.

Helper T-cell

A type of lymphocyte that secretes interleukins, a protein that triggers the action of other cells, including the attack of foreign cells by the cytotoxic T cell.

Cytotoxic T cells

The category of lymphocyte that attacks foreign cells.

Cytokines

Cell signaling molecules released primarily by helper T-cells and macrophages. Certain cytokines activate cytotoxic T-cells.

What do helper T cells produce?

Cytokines to activate a cytotoxic T cell.

What does the cytotoxic T cell do?

Searches out and destroys any cell that contains pathogen’s antigen signature.

What can the helper T cell also do?

Activate B cells in response to a certain antigen. The helper T cell induces the B cell to multiply rapidly into secretory cells called “plasma cells.”

What do plasma cells do?

Produce large amounts of an antibody that can bind the antigen

Antibody

A blood protein that counteracts a specific antigen

What do B cells do?

Clone into memory cells, which allows the body to remember a specific antigen.

What happens when a remembered antigen appears again the body?

It triggers the memory cells to form plasma cells, which quickly produces the specific antibody to the antigen.

Memory cell

A lymphocyte that responds to an antigen upon reintroduction

What are the two (2) ways to protect the body?

Through passive and active immunity.

• Through either passive introduction of antibodies as a protective agent or its active production by the body.

How can both passive and active immunity be induced?

Artificially

• Vaccinations introduce antigens, which are weakened or killed, to elicit an immune response.

Active immunity

Protection against a specific pathogen resulting from the production of antibodies in response to the presence of specific antigens.

Passive immunity

Temporary immunity gained by a body that has acquired antibodies from an outside source that can rapidly neutralize toxins.

• Ex: rapid treatment for a snakebite

What are many diseases caused by?

A malfunction of the immune system.

• Underactivity of the immune system can cause components to be ineffective.

What is the acquired immune deficiency syndrome (AIDS) caused by?

The human immunodeficiency virus (HIV), which infects helper T cells and prevents them from activating cytotoxic T cells and B cells and prevents the adaptive immune system from operating.

What can an overactive immune system do?

It can target innocuous foreign particles like pollen, causing the body to overproduce huge amounts of antibodies that trigger a histamine release from mast cells, which results in allergy symptoms, such as sneezing and mucus secretion.

What can the immune system mistakenly do?

It can mistakenly target a host molecule as a foreign antigen, leading to autoimmune diseases, which are conditions in which the immune system mistakenly attacks the body.

Autoimmune disease

A pathology that results from the immune system mistaking part of the body as a pathogen.

Which are examples of autoimmune diseases?

Type I diabetes, rheumatoid arthritis, and multiple sclerosis.

Rheumatoid arthritis

A progressive autoimmune diseases that causes joint inflammation and pain.

What does the immune system work with other body systems for?

To transport immune cells, signaling molecules, and antibodies throughout the body.

Examples:

• the circulatory system transports white blood cells throughout the body

• the lymphatic system produces white blood cells or lymphocytes

• The vessels in the lymph system drain fluid from body tissues and deliver foreign material to the lymph nodes to be processed by lymphocytes

• Red bone marrow, found in many bones of the skeletal system, also produce white blood cells

• The integumentary system functions as the first line of defense for most of the body.

Bone marrow

A soft material within spongy bone and medullary cavity of long bones.