AP2 Chapters 22: Lymphatic System

Spleen Functions

- Destroys defective RBCs -Detects and responds to foreign substances -Limited reservoir for blood

Activated complement proteins

- Form membrane attack complexes (MAC) that make channels through the plasma membrane -Attach to surface of bacterial cells, stimulate phagocytosis -Attract immune system cells to site of infection and promote inflammation

Tonsils

- Palatine (the "tonsils") -Pharyngeal (the "adenoids") -Lingual

Antibody-Mediated Immunity

--Effective against extracellular antigens including bacteria, viruses, protozoans, fungi, parasites, and toxins when they are outside cells. •Antibodies or Immunoglobulins (Ig) -Classes: IgG, IgM, IgA, IgE, IgD

Inflammatory Response types

--Local: confined to a specific area of the body. Symptoms are redness, heat, swelling, pain, loss of function -Systemic: occurs in many parts of the body. Same symptoms as local, but in addition: •Increase in neutrophil numbers released by red bone marrow •Fever due to production of pyrogens by various kinds of cells. Improves performance of immune system. •Widespread increased vascular permeability due to histamines. Large volume of plasma enters interstitial spaces leading to shock

Inflammatory Response

--Tissue injury regardless of type can cause inflammation •Response initiated by chemical mediators that produce vasodilation, chemotactic attraction, increased vascular permeability. The latter allows fibrinogen and complement to enter tissue. Fibrinogen converted to fibrin, walls off infected area.

Complement

-Group of 20 proteins that circulate in blood in inactive form and become activated in cascade form. In a Classical or alternative pathway.

Adaptive immunity Stimulant

-Haptens: small molecules, combine with large proteins and producing an adaptive immune response. •Types -Humoral or Antibody-mediated: B cells

Lymphatic capillaries

-More permeable than blood capillaries, -Epithelium functions as series of one-way valves, -Found in all parts of the body except nervous system, bone marrow, and tissues without blood vessels (cartilage, cornea, epidermis)

B and T cells

-Originate in red bone marrow -Move to primary lymphatic organs where they mature into functional cells: B cells to bone marrow and T cells to thymus -Secondary lymphatic organs and tissues: lymphocytes interact with each other, antigen-presenting cells and antigens to produce the immune response. •Diffuse lymphatic tissue, lymphatic nodules, tonsils, lymph nodes, spleen

Interferons

-Prevent viral replication (Viruses use the molecular mechanisms of cells to reproduce themselves). Interferons produced by infected cell, but cause neighboring cells to produce antiviral proteins, thus act as a paracrine.

Basophils and mast cells

-Promote inflammation when activated by innate or adaptive system. -Basophils are motile, leave blood and enter infected tissues -Mast cells are non-motile; in C.T.

Antibody-Mediated Immunity structure

-Variable region: Part that combines with antigenic determinant of antigen -Constant region: Responsible for activities of antibodies like activating complement or attaching to various kinds of WBCs.

Activation Antigenic determinant

-can occur in two ways -Antigenic receptors (T-cell receptors and B-cell receptors) •Surface of lymphocyte that combines directly with antigenic determinant -Activation involving glycoproteins called major histocompatibility complex (MHC) molecules attached to plasma membranes. Have variable region that can bind to foreign and self antigens.

Costimulation

1. By cytokines. Released by the macrophage of a cytokine that binds to a receptor on the helper T cell. 2. By surface molecules. Binding of two molecules (B7 and CD28) on the macrophage and Helper T cell. Helps to hold the cells together.

Activation of Lymphocytes

1. Lymphocytes must be able to recognize the antigen 2. After recognition, lymphocytes must increase in number to effectively destroy antigen

Immunity

Ability to resist damage from foreign substances such as microorganisms and harmful chemicals - Innate or nonspecific resistance

Adaptive immunity Stimulant

Antigens: large molecules

Lymphatic organs

Can be Encapsulated- lymph nodes, spleen, thymus

Lymphatic organs

Can be Nonencapsulated- mucosa-associated lymphoid tissue (MALT). Found beneath epithelium as first line of attack against invaders.

Lymphocyte Proliferation

Cells from original clones must proliferate before antigen can be attacked effectively

Negative selection

Eliminates clones of lymphocytes that react against self-antigens

Positive selection

Ensures survival of lymphocytes that react against antigens. These then proliferate and form clones.

Functions of the Lymphatic System

Fluid balance -Excess interstitial fluid enters lymphatic capillaries and becomes lymph (30L from capillaries into interstitial fluid, 27L return leaving 3L, called lymph). Fat absorption -Absorption of fat and other substances from digestive tract via lacteals. Fluid called chyme Defense -Microorganisms and other foreign substances are filtered from lymph by lymph nodes and from blood by spleen

Adaptive immunity Stimulant

Foreign: not produced by body, introduced from outside: -Bacteria, viruses, other microorganisms that cause disease -Pollen, animal dander, feces of mites, foods, drugs cause overreaction of immune system called allergic reaction.

Class II Major Histocompatability Complex (MHC)

Found on surface of antigen-presenting cells. B-cells, macrophages, monocytes and dendritic cells. Display of MHCII with foreign antigen is like "Rally round the flag", stimulates other immune system cells to respond to the antigen.

Class I Major Histocompatability Complex (MHC)

Found on surface of nucleated cells. In concert with antigens that were produced inside the cell from, for example, digested virus particles. Like displaying a flag saying "Kill me!" MHC-restricted: both MHCI and foreign antigen are displayed together

Cell-Mediated Immunity

Function of T cells; most effective against intracellular microorganisms: viruses, fungi, intracellular bacteria, parasites function in two ways: -Lyse virus-infected cells, tumor cells, and tissue transplants. Major lysin is perforin, which forms a hole in the plasma membrane of the target cell. -Produce cytokines, which promote phagocytosis and inflammation memory cells are produced. Delayed hypersensitivity T cells. Involved in allergic reactions; e.g., poison ivy. Hapten that binds to proteins in the skin, then antigen processed by Langerhans cells (APCs) of the skin and presented t

Costimulation

In order for B or T cells to produce a response, there must be binding of the MHC class II/antigen complex to the T cell receptor If costimulation does not take place, cell exhibits anergy (B or T cell does not respond to an antigen). Usual situation where anergy occurs is when T cell encounters a self antigen

Adaptive Immunity

Involves the ability to recognize, respond to, and remember a particular substance

Tonsils

Large groups of lymphatic nodules in nasopharynx and oral cavity •Provide protection against bacteria and other harmful material. Form a ring around the border between the oral cavity and the pharynx

Spleen

Located in left superior side of abdomen •Can be ruptured in traumatic abdominal injuries resulting in bleeding, shock, death •White pulp associated with arteries; red pulp with veins •Periarterial lymphatic sheath and lymphatic nodules contain lymphocytes, macrophages. •Splenic cord: reticular cells producing reticular fibers. •Blood flows through at 3 different rates -Fast (most), slow, intermediate -Slow flow is via open circulation: no direct capillary connection between arteries and veins. Blood percolates through splenic cords.

Thymus

Located in superior mediastinum; grows rapidly during first year, then stays same size through adulthood. Decreases in size after 60 years. •No reticular fibers: internal network formed by epithelial cells with long processes. •Cortex (numerous lymphocytes) and medulla (fewer lymphocytes) •Site of maturation of T cells: many T cells produced here, but most degenerate. Those that remain can react to foreign substances, but not to healthy body tissue.

Neutrophils

Phagocytic and first cells to enter infected tissue; last only a few hours. -Regularly cross wall of gastrointestinal tract, providing protection. 126 billion/day

Innate or nonspecific resistance

Physical barriers: prevent entry or remove microbes. Skin, tears, saliva, mucous membranes, mucus. Considered the acid mantle Physical barriers -Skin, mucous membranes -Cilia in respiratory tract -Coughing and sneezing •Chemical mediators: promote phagocytosis and inflammation •Cells: involved in phagocytosis and production of chemicals -Adaptive or specific immunity

Aging of Immune System

Primary and secondary responses decrease •More antigen required to produce a response, slower, less antibody, fewer memory cells produced •Ability of cell-mediated immunity to resist intracellular pathogens decrease; e.g., influenza •Reactivation of pathogens; childhood chicken pox virus causes shingles (herpes zoster)

Antibody Production primary

Primary response: occurs when a B cell is first activated by an antigen. B cell proliferates to produce plasma cells (antibody production) and memory cells.

Fine collagen reticular fibers

Produced by reticular cells. Act as filter to trap microorganisms and other particles -May be encapsulated or not

Antibody Production secondary

Secondary response: occurs during later exposure to same antigen. Memory cells divide rapidly to form plasma cells and additional memory cells. Faster and greater response.

Adaptive immunity Stimulant

Self-antigens: produced by your body. Used as markers to allow adaptive immune response to differentiate self from non-self. -Response to self tumor antigens helpful -Response to self-antigens resulting in tissue destruction: auto immune diseases

Lymph Nodes

Superficial and deep. •Organized into cortex and medulla with dense connective tissue capsule surrounding. Trabeculae extend within. Reticular fibers form supporting network. •Only structures to filter lymph •Afferent and efferent vessels •Substances removed by phagocytosis or stimulate lymphocytes to proliferate in germinal centers. •Cancer cells often migrate to lymph nodes, are trapped there, and proliferate. Can move from lymphatic system to circulatory system spreading cancer through body.

Innate Immunity

White blood cells: most important cellular components of immune system. Must be able to move into infected tissues and destroy infection

•Specific

ability to recognize a particular substance. •Memory: ability to remember previous encounters with a particular substance and respond rapidly

Acquired Immunity Immunization

deliberate exposure to antigen or antibody

Lymphatic nodules

denser aggregations. Numerous in loose connective tissue of digestive (Peyer's patches), respiratory, urinary, reproductive systems (MALT) Referred to as lymphatic follicles when found in lymph nodes and the spleen

Diffuse lymphatic tissue

dispersed lymphocytes, macrophages; blends with other tissues. Associated with other types of lymphatic tissue

Lymph nodes

distributed along vessels and filter lymph

Lymphatic ducts

drains body tissues and move lymph into major veins -Right side: drains right side of head, right-upper limb, right thorax -Thoracic side: drains remainder of the body

Lymphatic vessels

have valves that ensure one-way flow

Alternative pathway

is part of innate immunity. C3 binds with foreign substance. Attract macrophages.

Lymphatic capillaries

join to form lymphatic vessels

Lymphatic trunks

jugular, subclavian, bronchomediastinal, intestinal, lumbar

Macrophages

large phagocytic cells -Monocytes that leave blood, enter tissues. Longer-lived than neutrophils, can ingest larger particles -Found beneath free surfaces within sinuses (spleen, bone marrow, liver, lymph nodes).

Eosinophils

leave blood and enter tissues -Reduce inflammation by breaking down chemicals produced by basophils and mast cells. -Secrete enzymes that kill some parasites.

Lymphatic organs contain

lymphatic tissue: -Lymphocytes, -Fine collagen reticular fibers, -can be encapsulated and nonencapsulated

lymphatic tissue

lymphocytes, macrophages, dendritic cells

Chemotaxis

movement toward the source of chemotactic factors (parts of microbes or chemicals act as chemical signals and attract WBCs) -Phagocytosis: endocytosis by neutrophils and macrophages

MALT

mucosa-associated lymphoid tissue

Active natural immunity

natural exposure to an antigen

Classical pathway

part of adaptive immunity. that requires antibodies bound to antigens.

Antigenic determinant

specific regions of a given antigen recognized by a lymphocyte

Tolerance

state of unresponsiveness of lymphocytes to a specific antigen, usually to self antigens (one's own cells). •Many, many different kinds of clones exist because of genetic recombination during development.

Tolerance

state of unresponsiveness of lymphocytes to a specific antigen. Most common is unresponsiveness to self antigens. Provoked by -Deletion of self-reactive lymphocytes -Preventing activation of lymphocytes that encounter self antigens -Activation of suppressor T cells: cells that may produce suppressive cytokines or kill antigen-presenting cells. Poorly understood.

Passive artificial immunity

transfer of antibodies (or cells) from an immune animal to a nonimmune one -Antiserum -Available for rabies, hepatitis, measles; toxins formed by bacteria such as tetanus, diphtheria, botulism; venoms from poisonous snakes and black widow spiders

Passive natural immunity

transfer of antibodies from a mother to her fetus or baby

Natural killer cells

type of lymphocyte -Lyse tumor and virus-infected cells -Recognize whole classes of cells, not specific kind

Active artificial immunity

vaccination. Deliberate exposure to an antigen (vaccine)

Lymphocytes

white blood cells derived from bone marrow, but may mature and reside elsewhere

Lymph

•Water plus solutes from two sources: -Plasma: ions, nutrients, gases, some proteins, -Cells: hormones, enzymes, waste products, •Returns to circulatory system via veins; essential for fluid balance.