Immune System Flashcards
What is lymph
Made of mostly water/plasma
- Returns interstitial fluid that leaked out back into the bloodstream
-> returned to blood via lymphatic ducts
-> important in maintaining BP and blood volume
Other components
- leukocytes
- proteins
- electrolytes
- urea, creatine, other waste products
How are lymph vessels different from veins
Lymphatics have thinner walls than veins
-> collapse easily under pressure
How is lymph absorbed?
1st absorbed at capillary levels
Capillaries-> precollectors-> collectors-> trucks-> ducts
collectors have smooth muscle and valves
- right lymphatic duct drains from RUQ
- thoracic duct drains from rest of body
Cisterna chyli
Collects lymph from abdomen and drains into thoracic duct
-lymphatic ducts return lymph fluid to subclavian veins
How does lymph move?
Filtration and Diffusion
Additional Mechanisms
- Nerve stimulation
- Mild stimulation of dermal tissue
- Arterial pulsation adjacent to lymph vessel
- Muscle contraction adjacent to lymph vessels (skeletal muscle pump)
- Abdominal/thoracic cavity pressure (respiratory pump)
Lymphangion
Functional unit of lymph vessel
- portion of vessel b/w adjacent valves
Contain smooth muscle in walls; intrinsic (self-regulating) pumping mechanism triggered by pressure in the vessel
What are lymph nodes?
Found in groups along lymph vessel (encapsulated, 1-2cm)
-> enters through Afferent lymph vessels and leaves via efferent lymph vessels
Filters lymph (metal detectors)
- MACROPHAGES phagocytized bacteria and foreign materials
- plasma cells develop from B lymphocytes exposed to pathogens in lymph and produce ANTIBODIES
plasma cells make antibodies
Macrophages and B cells are security guards
Lymph Nodules
Much smaller than nodes
- > no capsule
Located beneath epithelium of mucous membranes
Found in…
- Respiratory tract
-> Tonsils: lymph nodules in pharynx
- Digestive tract
-> Peyer’s patches: lymph nodules in small intestines
- Urinary tract
- Reproductive tract
What does the spleen do?
Produces RBCs in fetus
After birth functions…
- Filters blood that flows through it
- Contains plasma cells, producing antibodies
- Contains monocytes and fixed macrophages that phagocytize pathogens or foreign material in blood
-> Monocytes enter when tissue is damaged and needs cleanup and repair
- Stores platelets and destroys them when no longer needed
Monocytes are baby macrophages
What happens in the thymus
Located inferior to thyroid (gets smaller as we age)
- Stem cells of thymus make T lymphocytes aka T cells
Thymus University
- Immature T cells are “introduced” to the cells and organic molecules of the body
-> develop self recognition and self tolerance
What is innate immunity?
-Non specific response
- Chemical secretions
- Mechanical barriers
- Mucous membranes
- Tears
- Saliva
- Phagocytosis
- Inflammatory response
- Efficiency does NOT increase with repeated exposure
What is Adaptive Immunity?
- Specific
- Carried out by lymphocytes and macrophages
- Key mechanisms
- cell mediated and antibody mediated immunity - becomes more efficient with repeated exposure
Two Types…
1. Cell mediated immunity (CMI)
-> Develops when T cells w/ protein receptors on cell surface recognize antigens on target cells -> destroy invading antigens
- reproduce to create more cells to battle the antigen
2. Antibody mediated (humoral) immunity
-> B cells become plasma cells after exposure to antigens
Self Antigens
- Cell surface antigens; found on cell membrane
- HLA complex: group of genes coding for production of specific proteins
-> helps immune system distinguish body’s own proteins from foreign substances
-> Normally, immune system ignores self cells/antigens because of self recognition and self tolerance
Non-Self Antigens
-Immune system recognizes specific non-self antigens as foreign
-Development of specific response to that particular antigen
-Memory cells produced respond quickly to antigen when encountered again
Mast cells
Release histamine and other chemical mediators in inflammatory response
Neutrophils
Phagocytosis; active in inflammatory process
Basophils
play major role in allergic reactions; release histamine; bind to IGE
Eosinophils
Involved in allergic reactions; phagocytosis, antiparasitic and bactericidal activity
Monocytes
Circulate in blood; mature into macrophages upon migration into tissues in response to infection/inflammation (baby macrophages)
Macrophages
Phagocytosis; process and PRESENT antigens to lymphocytes for immune response
-present throughout body (develop from monocytes)
-initiate immune response
-Engulf foreign material
-> process and display foreign antigen material on the cell membranes
-> lymphocytes respond to display, triggering immune response
-secrete chemicals
Dendritic cells
Phagocytosis; antigen PRESENTING cells
Lymphocytes
- T cells: originate in bone marrow, mature in thymus
- B cells: originate AND mature in bone marrow
- Natural Killer cells
come from lymphoblasts
What are cytotoxic T killer cells
Bind to antigen and release cytotoxic enzymes/ chemicals (destroy pathogens)
Produces cytokines to attract macrophages
What are helper T cells
Regulate all the cells of the immune system via secretion of “messenger” cytokines
Activate B cells and cytotoxic T cells
What are Memory T cells
Remain in lymph nodes for years, respond if exposed to same antigen in future
- remember specific antigens -> faster secondary response
Regulatory T cells
Suppress immune response when no longer needed (breaks of the system)
What do B cells do? And what are the diff types?
Responsible for production of antibodies
Most involved in fighting bacteria and viruses that are outside of cells
-Plasma cells: product antibodies
-B memory cells: can quickly form clone of plasma cells
What do Natural Killer Cells do?
Destroy tumor cells, cells infected with viruses, and other foreign cells without need for prior exposure
- localized to infected tissue in response to cytokines
What are Antibodies
Aka immunoglobulins
- Found w/in general circulation and lymphoid tissues
- 5 major classes (GAMED)
- Constant region
-> attaches to macrophages and other effector cells, related to type/class of immunoglobulin
-> determines mechanism used to destroy an antigen (IG) - Variable region
-> unique set of antibodies that binds to a specific antigen
-> gives antibody its specificity for a given binding antigen
IgG
- Most ABUNDANT antibody
- found in blood and Extracellular fluid
- Includes antiviral, antibacterial, and antitoxin antibodies
- Crosses placenta, creates passive immunity in newborns
IgM
- QUICKEST to respond/ increase immune response
- bound to B cells
- doesn’t require helper T cells
- Involved in ABO blood type incompatibility reaction
IgA
- Provides localized defense
- Found in secretions
- Tears
- Saliva and mucous membranes
- Colostrum
IgE
- Binds to mast cells or basophils in skin and mucous membranes
- Involved in allergic response
-> causes release of histamine and other chemical mediators - Results in inflammation
IgD
- Attaches to B cells
- Activates B cells and assists them in leaving bone marrow
What is the Complement System?
Group of inactive proteins circulating in blood (C1-C9)
Activated in innate and adaptive immune response
- When antigen-antibody complex binds with C1, it sets off a cascade of rxns
-> ultimately cause cell damage and further inflammation when activated (protective response)
Explain the Process of Adaptive/Acquired Immunity
2 step process
Primary Response
- occurs with 1st exposure of antigen
- Antigen recognized -> antibody production or sensitization of T cell occurs
- 1-2 weeks before antibody level reaches full efficacy
Secondary Response
- repeat exposure of same antigen
- more rapid response, with efficacy in 1-3 days
What is passive natural/natural passive immunity?
Passage of antibodies from mother to baby via placenta and breast milk (IgG transferred)
- Protection of infant for the first few months of life or until weaned (very limited memory)
What is passive artificial/ artificial passive immunity?
Injection of antibodies or IV infusion
-> Short term protection
No memory
What is active natural/natural active immunity?
Natural exposure to antigen
Development of antibodies
- exposure to pathogen triggers immune response
has memory
What is Active artificial/artificial active immunity
Antigen purposefully introduced to body
Stimulation of antibody production
- immunization triggers immune response to form antibodies
has memory
What are the Body Defenses ?
1st line of defense
- Non specific, mechanical barriers, reflexes
- Unbroken skin and mucous membranes
- Secretions have enzymes to break down bacteria
2nd line of defense
- Non specific
- Phagocytosis
- Inflammation: limit effects of injury or harmful event in body
3rd line of defense
- specific
- antibody mediated or cell mediated immunity
-> T cells and B cells
What happens during Acute Inflammation?
Vasodilation
- relaxation of smooth muscles increasing diameter of arterioles
Hyperemia
- increased blood flow to area
Increase in capillary permeability
- allows plasma proteins to move into interstitial space along with more fluid
Chemotaxis to attract leukocytes
- Movement of a substance or cell in response to a chemical stimulus
What are the Cardinal Signs of Inflammation?
Redness
1. Redness
- Increase blood flow to damaged area
2. Warmth or heat
- increased blood flow to damaged area
3. Swelling/edema
- increased capillary permeability, protein shift secondary to increase cap. Perm
4. Pain
- increased pressure on nerves, prostaglandins
5. Loss of function
- lack of nutrients of cells, edema and pain interfere with motion
What are the Systemic Effects of Inflammation?
- Mild fever (pyrexia)
- common if inflammation is extensive
- Increased WBCs
- Increased SED (ESR) - Malaise: general feeling of being unwell
- Fatigue
- Headache
- Anorexia (loss of appetite)
What happens in Chronic Inflammation?
- Less swelling
- presence of more lymphocytes, macrophages, and fibroblasts
- More tissue destruction
- More scarring
- Granuloma may develop around foreign object
-> small mass of cells with necrotic center, covered by connective tissue
What are some Complications of Inflammation?
- Infection
- Microorganisms can easily penetrate edematous tissues
- resist phagocytosis - Muscle spasm
- protective response to pain - Ulcerations
- caused by cell necrosis and lack of cell regeneration causing erosion of tissues
-> can lead to perforation of viscera or scarring - Immune suppression
- further increases infection risk
What are the types of Healing?
- Resolution
- occurs when there is minimal tissue damage
- damaged cells can recover
- tissue returns to normal w/in a short time
EX: mild sunburn - Regeneration
- occurs in damaged tissues where cells are capable of mitosis
(Epithelial cells are constantly regenerating)
- nearby cells may proliferate to replace the damaged cells/tissues with identical ones - Replacement
- Occurs with extensive damage or when cells are incapable of mitosis (cardiac and brain tissue)
- functional tissue replaced with scar tissue (fibrous tissue)
- loss of function
- chronic inflammation and infection lead to more scarring
