Chapter 4 - The Immune System and Immunity

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What is inflammation?

An immediate response that occurs when foreign or injurious agents are allowed into the cells or tissues of the body

What are cells and chemical products produced during the inflammation process essential for?

Essential in activating another of the body's defenses, the immune system

What is the goal of the immune system?

To prevent foreign substances from entering the body and to establish immunity or resistance to disease-producing agents, such as bacteria and viruses, through the immune response

What is an antigen?

The agent that triggers the immune response

What can antigens be?

Chemicals, food proteins, products of microbes, microbes, abnormal human tissue, donor tissue cells, or the person's own normal tissue cells

What are usually large weight substances, such as proteins and polysaccharides?

Antigens

What are smaller weight substances, such as some metals, the oils from poison ivy leaf, and some medications such as penicillin, called?

Haptens

Haptens can only exhibit antigenic properties when combined with what?

A larger human protein from the skin, blood, or other tissue

What can trigger an immune response without the help of human protein?

Large molecular weight substances such as lipopolysaccharides

What does the immune system cells need to be able to distinguish between?

Self and non self

How does the body distinguish between self and non-self?

By coding each cell surface with molecules that are equivalent of an identification tag

What are molecular identification tags called?

Major histocompatibility complexes (MHC)

Where are MHC found?

On almost every cell that has a nucleus

What is another name for MHC?

Human leukocyte antigens (HLA)

What does MHC play an important role in?

Activating the immune response

What can cause the MHC of a particular cell to change?

Injury, viral infection, or other stimulus

What will MHC become when it changes?

MHC will become antigenic and the cell will no longer be recognized by the immune system as self

What happens when the cell is no longer recognized by the immune system as self?

Change initiates the immune response, which results in destruction of the cell

What plays a vital role in organ and tissue transplantation?

MHCs

What must be matched as closely as possible to minimize the potential for rejection of the transplant?

The MHC molecules of organ and tissue transplant recipients and their donors

What is nonspecific immunity?

Defense mechanisms that are nonspecific meaning they require no previous exposure to the offending agent to accomplish their objective of neutralizing that agent

What is another name for nonspecific immunity?

Innate immunity

What are examples of nonspecific immunity?

Physical barriers, chemical barriers, nonspecific phagocytes, indigenous microbes that compete with pathogens, inflammatory response, clotting system, and complement and kinin systems

What are included in physical barriers?

Integumentary system, skin and mucous membrane; Waldeyer's ring; nasal hairs and sneezing; respiratory tract cilia and coughing

What are included in chemical barriers?

pH of the skin; mucous secretions; gastric acids; tears, sweat, and saliva

What are included in nonspecific phagocytes?

Monocytes, macrophages, and neutrophils

What are an integral part of nonspecific immunity?

Inflammatory process, kinin, clotting, complement systems, and the actions of some of the phagocytic cells

What is essential in activating or enhancing the immune process that results in resistance to specific antigens or specific immunity?

Chemical mediators involved in or secreted by the phagocytic cells are essential in activating or enhancing the immune process

What are the two forms of immunity that helps maintain the body in a healthy state?

Nonspecific and specific immunity

What is another name for specific immunity?

Acquired immunity

How does specific immunity work?

Specific immunity acts against previously encountered agents with antibodies and activated lymphocytes that are specific for that agent

What is an immune response?

When specific immunity acts against previously enountered agents with antibodies and activated lymphocytes that are specific for that agent

How is the immune response carried out?

By the immune system

What does the immune system work in conjunction with?

The inflammatory and the healing and repair processes of the body to maintain the health of the individual

What are the principal organs of the immune system?

Bone marrow, thymus, spleen, lymphatic vessels and nodes, and mucosa associated lymphoid tissues

What does the bone marrow produce?

All of the cells of the immune system from precursor stem cells

What is the function of the thymus?

To educate some of these cells, called T cells, to make them self tolerant

What is self tolerance?

Having the ability to recognize the host's own cell as self

What are the functions of the spleen?

Serves as a filer to remove old and damaged red blood cells from the general circulation, and as part of the immune system; will mount an immune response against any foreign substance presented to it via the same circulating blood

What is the function of the lymphatic system?

Initiate an immune response , process some of the immune system cells, called B cells, and remove foreign substances from the host through a system of vessels and nodes placed throughout the body

What are numerous strategically placed mucosa associated lymph tissues important for?

Maintaining the immune status of the individual by detecting and removing injurious substances before they compromise this defensive barrier

Where are the mucosa associated lymph tissues located?

In the gastrointestinal, respiratory, and genitourinary tracts

What is the most notable lymph tissue?

Waldeyer's ring

Where is Waldeyer's ring located?

In the oral pharyngeal area

What is the Waldeyer's ring composed of?

The adenoid or pharyngeal tonsil and the lingual and palatine tonsils

What is the immune system consist of?

Chemical molecules and immune cells that inhabit lymphatic tissue and circulate in body fluids

What do the cells of the immune system include?

Macrophages and lymphocytes

What are lymphocytes?

White blood cells found in lymphoid tissues

What are the two categories of lymphocytes?

B lymphocytes and T lymphocytes

What is B lymphocytes most active in?

Humoral immunity

What is T lymphocytes most active in?

Cell mediated immunity, even though they are also necessary for the optimal functioning of humoral immunity

What are cytokines?

A complex system of chemical molecules

What produces cytokines?

Immune cells

What is the function of the cytokines?

Modulates and regulates how the system responds to a stimulus; various functions such as carrying messages to and from cells, enhancing cell growth, stimulating chemotaxis, and activating immune cells

What is the goal of the immune response?

To remove or neutralize antigenic substances

How does the immune response accomplish its goal to remove/neutralize antigenic substances?

System must recognize the "invader", react to the invader, and remember the invader

What are the two interactive components of the systemic immune system?

Humoral response and cell mediated cellular response

What is humoral immunity provided by?

B lymphocytes or B cells

Where are B cells developed?

In the bone marrow and then mature in lymphoid tissue throughout the body

What does the maturation process ensure?

The surface of each B cell contains an antibody

What is an antibody?

A molecule that will react against one or more specific types of antigen

What is the antigen-binding fragment (Fab)?

The part of the antibody that combines with or binds to an antigen

When does the B cell becomes activated?

When its antigen-binding fragment comes in contact with an antigen that it can bind to

What must bind to the B lymphocyte before it can become activated?

T helper cell

What is the end product of the B cell activation?

The transformation of the B cell into an antibody-secreting lymphocyte known as a plasma cell

Both B and T cells must function together before what happens?

A plasma cell can be created and antibodies porduced

How long do plasma cells live?

Only a few days

What does the process of B cell activation stimulate?

Stimulates the plasma cells to divide and become more numerous, which increases the amount of antibody produced

What is the bone marrow stimulated to produce?

More B cells that can become plasma cells upon activation

How long does it take to build up enough circulating antibody to inactivate most antigens after initial exposure?

About 2-3 weeks

What is the primary immune response?

The few weeks it takes for enough circulating antibody to inactivate most antigens after initial exposure

The slow production of antibody at the initial exposure results in what?

The host usually showing some overt signs and/or symptoms of the specific pathology or disease associated with that antigen

What is a memory B cell?

Another type of B lymphocyte

When is a memory B cell created?

As the primary immune response is terminated

Why do memory B cells carry the description of the antigen?

So that it will be recognized more quickly and acted against more rapidly the next time the antigen is encountered

If the host survives the primary encounter with the antigen, what will happen during the second exposure?

A second exposure will activate the memory B cells, which initiate an immediate, full immune response to the antigen

What is a secondary immune response?

When a second exposure will activate the memory B cells, which initiate an immediate, full immune response to the antigen

How long can memory cells live for?

Decades

What are memory cells ready to do?

To mount an immediate antibody assault when triggered by a "remembered" antigen

What are various ways in which antibodies attack circulating antigens?

1. Neutralize bacterial toxin
2. Bind with viruses to prevent entrance into cells
3. Cause the agglutination or clumping of antigens to facilitate phagocytosis
4. Bind to the surfaces of the antigen to aid in phagocytosis (opsonization)
5. Bind with an antigen to activate the complement system which then inactivate the antigen

What are the 5 major groups of antibodies or immunoglobulins?

IgG, IgM, IgA, IgE, IgD

What are immunoglobulins produced by?

The B lymphocytes

What is IgG?

Gamma globulin which is a circulating antibody and is directed against common infectious agents such as viruses, bacteria, and toxin

What does IgG bind to?

It binds to the antigen and then binds to a surface receptor on a phagocytic cell allowing for phagocytosis of the antigen-antibody complex

What allows for the phagocytosis of the antigen-antibody complex?

IgG binding to a surface receptor on a phagocytic cell

What does IgG activate?

The classic pathway of the complement system and is active in the secondary immune response

What is the only immunoglobulin that crosses the placental barrier and protects the developing child and newborn until his or her own immune system matures?

IgG

What makes up 80% of the circulating antibodies in the adult body?

IgG

How many types of IgG are there?

4

Where is IgM found?

On the surface of B cells

Which immunoglobulin is the largest of the immunoglobulins>

IgM

How many antigen-binding fragments can IgM have up to?

10 antigen binding fragments available for use

What is the first antibody produced in response to an antigen?

IgM

What is the main purpose of IgM?

To cause clumping or agglutination of antigen proteins during the primary immune response

What is agglutination?

Clumping

Which immunoglobulin is most efficient in activating the classic pathway of complement system?

IgM

Where is IgA found?

In secretions such as saliva, tears, and mucus of respiratory, gastrointestinal, and genitourinary tract

How many types of IgA are there?

2

What is IgA secreted by?

Plasma cells located in the epithelium of associated tissues

What do the secretions from plasma cells form?

Part of the primary defense mechanism of the body by preventing the attachment of the pathogens to epithelial ccells

What can IgA activate?

The alternative pathway of the complement system

What can be found in breast milk and can help protect the newborn infant?

IgA

What is IgE secreted by?

Plasma cells in the skin and mucous membrane

What does IgE trigger?

The release of histamine from mast cells and basophils and is important in the inflammatory response

Which immunoglobulin is responsible for the symptoms of immediate hypersensitivity allergic reactions

IgE

Which immunoglobulin helps protect the body from some parasitic infection?

IgE

What does an antigenic substance on the surface of the intestinal worms stimulate the release of?

Histamine from mast cells in the intestinal mucosa

What does histamine increase the permeability of?

Intestinal lining causing diarrhea, which is meant to result in expulsion of the worms

Where is IgD found?

On B lymphocytes cell surfaces

What immunoglobulin is associated with IgD?

IgM

What is the function of IgD?

It has regulatory effect on the functioning of the B cell

The humoral response uses what to accomplish its goal?

Antibodies

Antibodies in the humoral response cannot interact with what kind of cells?

Cells that have been infected with a virus or have become abnormal in any other way

What response can have antibodies interact with cells that have been infected with a virus or have become abnormal in any other way?

cellular or Cell mediated response

What is cell mediated immunity specific for?

Host cells (target cells) that have been infected with viruses or have been mutated and are possible sources of harm for the individual

What is the end result of cell mediated immune response?

Destruction of the target cell

What is another name for host cell?

Target cell

Cells involved in the cell mediated response are always what kind of cells?

Lymphocytes and include: T lymphocytes, natural killer cells, and macrophages

Where do T lymphocytes develop?

In the bone marrow from the same precursor or stem cells from which B lymphocytes developed

Where do the T lymphocytes mature (become self tolerant) and differentiate (become antigen specific)?

In the thymus

Where do B lymphocytes mature?

In lymphoid tissue

Where are T lymphocytes stored?

In lymphatic tissue all over the body

T cells must be what to function?

Activated

When does activation of T cells occur?

When an antigen presenting cell (APC) phagocytizes or otherwise binds to an antigen and brings it to the T cell

What are the most common antigen presenting cells?

Macrophages, monocytes, and B cells

What happens after the APC presents its antigen to the T cell?

The T cell is activated against that antigen

What cytokines assists in the activation of the T cells?

Interleukins

What does the activation of T cells stimulate?

Stimulates the T cell to divide and produce several types of T lymphocytes that are specific for the activating antigen

T cells that can live for long periods of time and maintain their antigenic specificity become what?

T memory cells

What determines the T cell functions?

Protein molecules carried on the T cell surfaces, which are called clusters of differentiation

What are clusters of differentiation?

Protein molecules carried on the T cell surfaces

What cluster designations of T cells are significant?

CD4+ (T helper cell) and CD8+ (T cytotoxic cell)

What do T helper cells regulate?

The action of all the other cells of the immune system

What do T helper cells increase or enable the functioning of?

B lymphocytes, macrophages, natural killer cells, and other T cells by the release of cytokine

Humans normally have twice as many what cells circulating in the blood as what cells?

Twice as many T helper cells compared to T cytotoxic cells

What is another name for T helper cells?

CD4+

What is another name for T cytotoxic cell?

CD8+

What are T cytotoxic cells able to do with cells that have been recognized as being antigenic?

T cytotoxic cells are able to kill cells that have been recognized as antigenic

What are examples of antigenic cells?

Cells infected with viruses, cancer cells, and sometimes normal cells that the body has confused as nonself

What activated cytotoxic cell?

A T helper cell or macrophage before it can bind to and destroy the antigen

Where are cytotoxic cells active?

In tissue and organ rejection

What are natural killer (NK) cells similar to?

Cytotoxic T lymphocytes

What is the difference between cytotoxic T lymphocytes and natural killer cells?

Natural killer cells do not need to sensitized to an antigen before reacting with that antigen; they have the ability to recognize foreign substances without any input from other cells or chemical mediators

What do NK cells do once they recognize virus infected cells and other abnormal cells?

destroys them

Nk cells can do what in the presence of foreign substances?

Respond immediately thus important role in immune system

Often NK cell functions are impaired in what?

Immune deficiency disorders such as AIDS

There is evidence that what plays an important role ind detecting and eliminating what?

cancer cells before they can multiply

What do macrophages provide a crucial cellular link to?

inflammatory process and the immune system response

What are macrophages?

Monocytes that have left the circulating blood to enter connective or other tissues where they develop into macrophages

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