Ch. 22 - Lymphatic System Flashcards
Leukocytes
white blood cells; formed in red bone marrow. 5 types are neutrophils, eosinophils, basophils, monocytes, and lymphocytes. most are housed in body tissues
monocytes
leukocytes that become macrophages when they leave blood and enter tissue
secondary lymphatic structures
t- and b-lymphocytes, macrophages, dendritic cells, and NK cells housed in lymph nodes, spleen, tonsils, MAL:, lymphatic nodules. Select organs house macrophages; some permanent named for location
dendritic cells are housed in…
epithelial layers of skin and mucosal membranes. dendritic cells are usually derived from monocytes and engulf pathogens and migrate into lymph.
Connective tissue houses…
mast cells. Mast cells are typically close to small blood vessels, and abundant in dermis and mucosa of resp. GI, and uro tracts and in CT of organs.
Cytokines
small proteins that regulate immune activity. they are produced by cells of both innate and adaptive immune system. They are chemical messengers released from one cell that binds to target cells to signal, control development and behavior of immune cells, regulate inflammation, or destroy cells. Can act of cells that release it (autocrine) local cells (paracrine) or distant cells (endocrine)
Innate Immunity
present at birth and protect against a variety of different substances (nonspecific). No prior exposure is necessary and respond immediately to potentially harmful agents. Include barriers like skin and mucosal membranes, and nonspecific cellular and molecular internal defenses.
Adaptive Immunity
acquired/ specific. Response to antigen involves specific T- and B- lymphocytes (a particular cell responds to one specific foreign substance but not another. Takes several days to be effective. 2 branches, cell mediated (t) and humoral (b)
first line of defense (innate immunity)
skin and mucosal membrane
second line of defense (innate immunity)
internal processes of innate immunity such as activities of neutrophils, macrophages, dendritic cells, eosino and basophils, and NK cells. Chemicals such as interferon and complement, and physiological processes such as fever and inflammation
Preventing entry
few microbes can penetrate skin; skin releases antimicrobial substances such as dermicidin, lysozyme, sebum, and defensins. Skin also has nonpathogenic flora of microorganisms that prevents growth of pathogenic ones.
Mucus membranes line body openings and release antimicrobial substances like defensins, lysozymes, and IgA. It is lined by harmless bacteria that suppress growth of virulent types.
Innate immunity cells (nonspecific)
phagocytic cells (includes neutrophils, macrophages, and dendritic cells, basophils and mast cells, NK cells, and Eosinophils
Phagocytic cells
neutrophils, macrophages, dendritic cells
Neutrophils
destroy engulfed particles; intake vesicle fuses with lysosome forming a phagolysosome that digests unwanted substances. Residue is released via exocytosis.
Dendritic Cells
destroy particles and then present fragments. The antigens are presented on dendritic cell surface for T-lymphocytes and is necessary for initiating adaptive immunity.
Macrophages
phagocytotic, makes a phagolysosome within cell. Can perform antigen presentation.
Proinflammatory cells
Basophils and mast cells
Proinflammatory cells
Basophils and mast cells
Basophils and Mast Cells
basophils circulate in blood and mast cells reside in CT, mucosa, and organs. They release granules containing chemicals that increase movement of fluid from blood to injured tissue. They serve as chemotaxic chemicals that attract immune cells (histamine, heparine). Eicosanoids released from cell membrane also increase inflammation.
Chemotaxic Chemicals
chemicals that attract immune cells. Includes histamine that increases vasodilation and capillary permeability and Heparin that acts as an anticoagulant.
Apoptosis-initiating cells
NK cells and eosinophils
NK cells
cells formed in bone marrow, circulate in blood, and accumulate in secondary lymphatic structures. They perform immune surveillance and destroy unhealthy cells (bacteria/virus infested, tumor cells, transplanted) They kill by releasing cytotoxic chemicals Perforin and Granzymes.
Perforin
creates a transmembrane pore in an unwanted cell to later cause apoptosis
Granzymes
enter pore and cause apoptosis of cell (shriveling)
Immune Surveillance
patrol the body, detect unhealthy cells
Eosinophils
attack multicellular parasites They degranulate (release enzymes and other toxic substances that can from transmembrane pores in parasites cells) They participate in immune responses of allergy and asthma, engage in phagocytosis of antigen-antibody complexes.
Recognition of microbes as foreign
foreign microbes are recognized for receptors. pattern recognition receptors (toll-like receptors) on cell surface bind to patterns on microbe surface.
Antimicrobial Proteins
molecules that function against microbes. Includes interferons and complement systems
Interferons
class of cytokines that nonspecifically impedes viral spread.
IFN-alpha and IFN-beta
produced by leukocytes and virus-infected cells; they bind to neighboring cells and prevent their infection and trigger synthesis of enzymes that destroy viral nucleic acids (inhibits synthesis of viral protein)
IFN-g
produced by t-lymphocytes and NK cells. Stimulates macrophages to destroy virus-infected cells
Complement System
group of over 30 plasma proteins. work along with complement antibodies. Identified with letter C and # (C2). Synthesized by liver, continuously released in inactive form. Activation occurs by enzyme cascade.
Complement Activation Pathways
Classical pathway: antibody attaches to foreign substance, then complement binds to antibody.
Alternative Pathway: Complement binds to polysaccharides of bacterial or fungal cell wall, especially potent against bacterial infections.
Opsonization
complement protein (opsonin) binds to pathogen, enhances likelihood of phagocytosis of pathogenic cell.
Inflammation
is enhanced by complement. Activates mast cells and basophils; attracts neutrophils and macrophages. Nonspecific response to ward off unwanted substances
Cytolysis
complement triggers splitting of target cell. Complement proteins form Membrane attack complex (MAC) that creates channel in target cell’s membrane causing lysis.
Elimination of Immune complexes
complement links antigen-antibody complexes to erythrocytes and they move to liver and spleen where they are stripped off.
Events of inflammation
- Release of chemicals to cause
- vascular changes like
- Recruitment of leukocytes that release cytokines stimulating leukopoiesis in marrow
- Delivery of Plasma Proteins
Inflammation step one: Release of Chemicals
Injured tissue, basophils, mast cells, and infectious organisms release chemicals such as histamine, leukotrienes, prostaglandins, chemotactic factors that initiate vascular response
Inflammation step two: Vascular changes
vasodilation, increased capillary permeability, increased endothelial expression of molecules for leukocyte adhesion.
Inflammation step three: Recruitment of leukocytes
Leukocytes release cytokines stimulating leukopoiesis in marrow and macrophages may release pyrogens. Recruits through three processes…
Margination: adherence of leukocytes to endothelial CAMs
Diapedesis: cells escape blood vessel wall
Chemotaxis: leukocytes migrate toward chemicals released from damaged, dead, or pathogenic cells.
Pyrogens
fever-inducing molecules released by macrophages
Inflammation step four: Delivery of plasma proteins to site
certain proteins are brought to infection site immunoglobins, complement, clotting proteins, and kinins
Clotting proteins
form clots that wall off microbes
Kinins
stimulate pain receptors, increase capillary permeability, increase production of CAMs by capillary cells. Kinins are produced from inactive kininogens and include bradykinin
Effects of inflammation
- fluid (exudate) moves from blood to injured or infected area
- fluid, proteins, immune cells eliminate pathogens
- vasodilation increased bloodflow
- contraction of vessel cells increases capillary permeability
- loss of plasma proteins decreases capillary osmotic pressure which decreases fluid reabsorption into blood. This extra fluid is taken up b lymphatic capillaries in the area (washing)
Washing
extra fluid from inflammation site is taken up by lymphatic capillaries that carries away debris for lymph node to monitor contents
How long does inflammatory response last
within 72 hrs inflammatory response slows and tissue repair begins as fibroblasts form new CT. Macrophages eat bacteria, neutrophils begin to die and host cells are damaged.