Chapter 21 The Lymphatic System and Immunity

pathogens

disease causing organisms

lymphatic system

Composed of a network of vessels, ducts, nodes, tissues and organs. Provides defense against infection.

immunity

the ability of an organism to resist a particular infection or toxin by the action of specific antibodies or sensitized white blood cells.

parasite

An organism that lives on or in a host and causes harm to the host

bacteria

single-celled organisms that lack a nucleus; prokaryotes

virus

A tiny, nonliving particle that invades and then reproduces inside a living cell.

retrovirus

An RNA virus that reproduces by transcribing its RNA into DNA and then inserting the DNA into a cellular chromosome; an important class of cancer-causing viruses.

lymph fluid

similar to blood plasma, but LOW in protein content; fluid that circulates through the body in lymph vessels and eventually enters the bloodstream

lymph nodes

Bean-shaped filters that cluster along the lymphatic vessels of the body. They function as a cleanser of lymph as well as a site of T and B cell activity

lymphatic nodules

small, localized clusters of dense tissue formed by lymphocytes and macrophages

primary lymph tissues/organs

red bone marrow and thymus

MALT (Muscosa-associated lymphoid tissue)

Aggregated lymphoid nodules; Distal small intestine (ileum);

Peyer's patches

collections of lymphatic tissue found in the submucosa of the small intestine

lymph organs

lymph nodes, spleen, and thymus gland

lymphoid tissue

Tissue composed of lymphocytes supported by a meshwork of connective tissue; includes tonsils, MALT appendix, and bone marrow

lymphatic vessels

large vessels with valves, which collect and carry lymph to lymph nodes

peristalsis

the involuntary constriction and relaxation of the smooth muscles of the intestine or another canal (e.g. lymph vessel), creating wavelike movements that push the contents of the canal forward.

lymphatic capillaries

Small, blind-ended lymph vessels that act like drain pipes which pick up lymph at tissues throughout the body

thoracic duct

receives lymph from the left side of the head, neck, chest, abdomen, left arm, and lower extremities; empties into the left subclavian vein

right lymphatic duct

collects lymph from the right side of the head and neck, the upper right quadrant of the body, and the right arm; empties into the right subclavian vein

cisterna chyli

an enlarged pouch on the thoracic duct that serves as a storage area for lymph moving toward its point of entry into the venous system

lymphedema

swelling due to an abnormal accumulation of lymph fluid within the tissues

microphages

Neutrophils and eosinophils
Leave the bloodstream
Enter peripheral tissues to fight infections

macrophages

Amoeboid cells that roam connective tissue and engulf foreign particles and debris of dead cells.; Phagocytize foreign substances and help activate T cells

dendritic cells

specialized white blood cells that patrol the body searching for antigens that produce infections; antigen-presenting cells

tonsils

masses of lymphatic tissue in the back of the oropharynx

palatine tonsils

located on each side of the soft palate (roof of mouth)

pharyngeal tonsil (adenoids)

posterior wall of nasopharynx

lingual tonsils

located on the back, base of the tongue

Appendix

A small, fingerlike extension of the large intestine's cecum; contains a mass of white blood cells that contribute to immunity.

Cervical lymph nodes

deep and superficial group in the neck
monitor lymph coming from head and neck

Axillary lymph nodes

superficial lymph nodes in the armpits

Inguinal lymph nodes

located in the inguinal (groin) area of the lower abdomen; receive lymph from lower limbs

Thymus

endocrine gland in the thoracic cavity above the heart where T lymphocytes mature.

thymosin

Hormone secreted by the thymus gland that stimulates the maturation of lymphocytes into T cells of the immune system.

lymphadenitis

inflammation of the lymph nodes

lymphadenopathy

any disease process affecting a lymph node or nodes

Spleen

An organ that is part of the lymphatic system; it houses lymphocytes, filters the blood, stores iron, and destroys old blood cells.

Innate Immunity

nonspecific defense mechanisms that come into play immediately or within hours of an antigen's appearance in the body

Adaptive Immunity

(specific immunity) aquired ability to recognize and destroy a specific pathogen or its products. Requires exposure of the immune system to the pathogen

Helper T lymphocytes

subset of T lymphocyte that enhance humoral and cell-mediated responses of the immune system

B lymphocytes (B cells)

lymphocytes which mature in the bone marrow and that are involved in the production of antibodies

T lymphocytes (T cells)

Lymphocyte that matures in the thymus and acts directly against antigens in cell-mediated immune responses.

Regulatory T cells

control the T-cell response; may function in preventing autoimmune reactions

Memory T cells

Once activated, T cells multiply and give rise to clone cells, some of which become memory T-cells. Memory T-cells recognize pathogen they have encountered before, allowing for a quicker immune response in a second exposure.

Memory B cells

Produced during a B cell response, but are not involved in antibody producing during the initial infection; are held in reserve for the rest of your life in case you encounter that pathogen again.

Antibodies

Protein that is produced by lymphocytes and that attaches to a specific antigen.

Complement proteins

proteins in blood that help destroy pathogens by coating them (acting as opsonins), or puncturing them in addition to stimulating mast cells and basophils. Part of the non-specific immune response

Lectin

A protein that binds a carbohydrate, commonly an oligosaccharide (e.g. mannose), with very high affinity and specificity. Act as opsonins. Activates the complement system.

Chemotaxis

Cell movement that occurs in response to chemical stimulus

emigration (diapedesis)

phagocytes squeeze through the blood vessel endothelium to reach the damaged area

perforin

One of the proteins released by cytotoxic T cells (and NK cells) on contact with their target cells. It forms pores in the target cell membrane that contribute to cell killing.

lymphotoxin

A secretion of lymphocytes that kills the target cells.

cytokines

a large family containing a number of substances, such as interferons, interleukins, and growth factors, that are secreted by certain cells of the immune system and have an effect on other cells. Can initiate, inhibit, increase, or decrease activity in other cells.

lymphokines

produced by T cells, direct the immune response by signaling between the cells of the immune system

interleukins

proteins (cytokines) that stimulate the growth/activity of B and T lymphocytes

opsonin

an antibody or other substance that binds to foreign microorganisms or cells, making them more susceptible to phagocytosis.

inflammation

a localized physical condition in which part of the body becomes reddened, swollen, hot, and often painful, especially as a reaction to injury or infection.

fever

body temperature above 37.2C

pus

A fluid created by infection.

necrosis

tissue death

Tumor necrosis factor (TNF)

Secreted by macrophages and T cells to kill tumor cells and regulate immune responses and inflammation

Respiratory burst (oxidative burst)

Phagolysosome (inside neutrophils) uses reactive compounds such as NO and hydrogen peroxide to destroy engulfed pathogens

clonal selection theory

States that the antigen selects which lymphocyte will undergo clonal expansion and produce more lymphocytes bearing the same type of receptor.
-Lymphocytes use 500 genes to produce a tremendous variety of specific receptors
-Undifferentiated lymphocytes undergo a continuous series of divisions and genetic changes that generate millions of different cell types
-Each cell has a particular/unique receptor specificity
-Lymphocytes that bind to self-antigens are triggered to undergo apoptosis

MHC I

protein complexes found on every nucleated body cell that can present foreign antigen; signals cytotoxic T to destroy particular antigen

MHC II

expressed on the surface of APCs (macrophages, dendritic cells, B cells) and functions by presenting antigen that is foreign in the body. Antigen is taken into the body by phagocytosis or endocytosis and is loaded onto MHC II within endosomes, and then expressed on the surface.

MHC

Major Histocompatability complex, a set of proteins found on the plasma membranes of cells that help display antigen to T cells. MHC I is found on all cells and displays bits of proteins from within the cell; this allows T cells to monitor cell contents and if abnormal peptides are displayed on the surface, the cell is destroyed by killer T cells. MHC II is found only on macrophages, dendritic cells, and B cells. This class of MHC allows these cells (known as antigen presenting cells) to display bits of "eaten" (phagocytosed or internalized) proteins on their surface, allowing the activation of helper Ts --> thus further activating immune response.

CD8 markers

Found on cytotoxic T cells and suppressor T cells
Respond to antigens on Class I MHC proteins

CD4 markers

Found on helper T cells
Respond to antigens on Class II MHC proteins

Active Immunity

A form of acquired immunity in which the body produces its own antibodies against disease-causing antigens.

Passive Immunity

An individual does not produce his or her own antibodies, but rather receives them directly from another source, such as mother to infant through breast milk or
Immunity conferred by transferring antibodies from an individual who is immune to a pathogen to another individual.

Artificially aquired active immunity

Occurs through the administration of a vaccine that contains an antigen. A vaccine stimulates a primary immune response against the antigen without causing symptoms of the disease

Artificially aquired passive immunity

A short-term immunity occuring through the administration, typically by injection or IV of antibodies that are not produced by the recipient's own immune cells. Immune Globulin or Gamma Globulin as it is more commonly known is an example of this.

naturally acquired active immunity

resulting from infection

Naturally acquired passive immunity

conferred by transfer of maternal antibodies across placenta or in breast milk

Haptens (Incomplete Antigens)

Small molecules (peptides, nucleotides, and hormones), not immunogenic by themselves, are immunogenic when attached to carriers, cause the immune system to mount a harmful attack.
Ex: Poison ivy, animal dander, detergents, and cosmetics.

Epitopes

the part of an antigen molecule to which an antibody attaches itself

Allergy

a specific reaction of the immune system to a foreign and frequently harmless substance

Anaphylaxis

Life threatening allergic reaction; a severe response to an allergen in which the symptoms develop quickly, and without help, the patient can die within a few minutes.

Allergen

a substance that causes an allergic reaction

histamine

a compound that is released by mast cells and basophils in response to injury and in allergic and inflammatory reactions, causing dilation of capillaries, increased capillary permeability, and at times, bronchoconstriction.