Set 8 Flashcards
What are the three types of components of the immune system?
- Lymphoid tissues
- Various types of immune cells
- Chemical signals that coordinate responses
What are the primary functions of the immune system?
- Protects against pathogens
- Protects against foreign molecules
- Removes dead or damaged cells
- Attempts to recognize and remove abnormal cells
What are the three types of immune system pathologies? Give an example for each.
- Incorrect immune response (e.g. autoimmune disease)
- Overactive immune response (e.g. allergy)
- Lack of immune response (HIV-AIDS immunodeficiency)
What are the two lines of body defenses?
1) Physical and chemical barriers
2) Immune defenses
What are physical barriers?
- Skin
- Mucous membranes
- Lacrimal apparatus (ducts secreting tears)
- Saliva
- Epiglottis
What are four chemical barriers?
- Sebum
- Perspiration
- Gastric juice
- Urine
How does sebum inhibit microbial growth?
Sebum, secreted by sebaceous glands, has a low pH, which inhibits microbial growth
How does perspiration inhibit microbial growth?
Flushes skin of microbes and contains lysozyme
What are the four steps in an immune response?
1) Detection and identification of the foreign substance
2) Communication with other immune cells
3) Recruitment of other immune cells, and coordination of the response
4) Destruction or suppression of the invader
What is the lymphatic system?
Vascular system that collects tissue fluid and returns it to the blood
What is the function of the lymphatic fluid?
- Lymph travels through lymphatic vessels
- At lymph nodes, they are screened for pathogens
- Then, they travel back into the venous system
Why are lymph nodes particularly concentrated in extremities?
Screening mechanism for the blood in the extremities prior to their re-entry into the heart
What are the two primary lymphoid tissues?
- Bone marrow
- Thymus
What are the two encapsulated lymphoid tissues?
- Lymph nodes
- Spleen
What are diffuse lymphoid tissues? Give an example.
- Unencapsulated lymphoid tissues and aggregations of immune cells that appear in other organs of the body
- Respiratory and digestive tract
- Ex: gut-associated lymphoid tissue (GALT), and tonsils
What is the structure of the thymus? Where is it located?
- 2-lobed organ
- Located in the thorax just above the heart
What occurs to the thymus during adolescence?
- Reaches its greatest size during adolescence
- Then, shrinks and is replaced with adipose
What occurs in the thymus during development?
Recognition and elimination of self-reactive cells
What peptides does the thymus produce to aid in T-cell differentiation?
- Thymosin
- Thymopoietin
- Thymulin
How do lymphoid nodules differ from lymph nodes?
Lymphoid nodules are NOT surrounded by a fibrous capsule
Where are lymphoid nodules located? How do they differ in size?
- Beneath epithelial lining of organs that have direct contact to the outside world (digestive, respiratory (tonsils), urinary)
- Size increases or decreases depending on the number of dividing lymphocytes
What allows the creation of lymphatic fluid?
- Capillary hydrostatic pressure is greater than blood osmotic pressure, which favours filtration
- Blood colloid osmotic pressure exerts a force to bring fluid back in
How do viruses differ from bacteria?
- Viruses are NOT cells
- Viruses must have a host cell to reproduce
What is the function of glycoproteins on viruses?
Their particular glycoproteins allow them to attach to certain specific types of cells
How do enveloped and non-enveloped viruses differ?
- Viruses with envelopes are very easy to kill with soap (ex: HIV, influenza)
- Non-enveloped viruses are less easy to kill
What are interferons?
Cytokines that inhibit viral replication and modulate the immune response
How are interferons produced? What occurs?
- Virus infected cell triggers the expression of interferons, and subsequently dies
- IFN is released and diffuses to a neighboring uninfected cell, and binds to receptor
- The binding triggers the expression of AVP, which degrade viral mRNA and stop viral replication
In a lymph node, where are B-cells and T-cells located?
- Outside: B-cells
- Middle: T-cells
What are the two functional regions of the spleen?
- Red pulp
- White pulp
What is contained within the red pulp region of the spleen?
- Extensive blood vessels
- Loaded with RBCs
What is contained within the white pulp region of the spleen?
- Resemble the interior of lymph nodes
- Mainly composed of lymphocytes
What are the three granulocytes?
- Neutrophils
- Basophils
- Eosinophils
What are the three agranulocytes?
- Monocytes and macrophages
- Lymphocytes
- Dendritic cells
What is the primary function of basophils and mast cells?
Release chemicals that mediate inflammation and allergic responses
What is the primary function of neutrophils?
- Ingest and destroy invaders
- Most common type of leukocyte
What is the primary function of eosinophils
Destroy invaders, particularly antibody-coated parasites
What are the primary functions of monocytes/macrophages?
- Ingest and destroy invaders
- Antigen presentation
What is the primary functions of plasma cells?
Specific responses to invaders, including antibody presentation
What is the primary function of dendritic cells?
Recognize pathogens and activate other immune cells by antigen presentation
Which leukocyte is specific to tissues? Give an example.
- Macrophages
- Ex: microglial cells in the brain
Are pathogens with capsules or without harder to kill?
Pathogens with capsules are harder to kill (virulence factor)
What must occur for the phagocytosis of pathogens with a capsule?
- The pathogen must be tagged with antibodies first
- Phagocytosis may then occur
What occurs to pathogens following ingestion?
- Phagosome contains ingested pathogen
- Lysosome contains enzymes and oxidants, which digest the pathogen
- Digested antigen
What leukocytes initiate adaptive immunity?
- Dendritic cells and other professional APCs
- They capture, process, and display antigens to the appropriate immune cells
What are the primary functions of natural killer cells?
- Induce apoptosis in infected cells
- Attack some tumour cells
- Secrete interferons
What is the function of IFN-a and IFN-B?
- Prevent viral replication
- At the beginning of a viral infection
What is the function of IFN-gamma?
- Activates macrophages and other immune cells
- At the end of a viral infection
What are three beneficial roles to inflammation?
- Attract immune cells and chemical mediators to sites of infection
- Create physical barriers to prevent infections from spreading
- Promote tissue repair
What is the function of acute-phase proteins? When are their levels elevated?
- Help prevent tissue damage
- Liver proteins that act as opsonins and enhance the inflammatory response
- In chronic inflammatory diseases
What do cytokines released upon tissue damage or infection trigger in mast cells?
Histamine
What vascular changes does histamine cause?
1) Vasodilatation (heat and redness)
2) Nearby capillaries become more permeable (edema)
Why does edema result from inflammation?
- Results from the osmotic effect of plasma proteins
- Plasma proteins in the blood normally bring blood back into capillaries, but if the plasma proteins are in the tissue, they do not exert this force and liquid stays out
What are cytokines?
Small proteins that stimulate or inhibit many normal cell functions, such as cell growth and differentiation
What are cytokines released by? What do they do?
- Released by tissue macrophages to stimulate inflammation
- Attract other immune cells, increase tissue permeability, and cause fever
What are interleukins? What do they cause?
- Subset of cytokines
- Cause fever
- Blood vessels become more permeable to WBCs and proteins
- Acute-phase proteins
What does bradykinin cause?
Pain and swelling
What do complement proteins cause?
- Complement cascade produces a membrane attack complex (MAC) that inserts into foreign cell membranes and results in cell lysis
- Creates pores in pathogens
What are chemotaxins?
Molecules that attract phagocytes to a site of infection
What are opsonins?
Proteins that coat pathogens so phagocytes recognize and ingest them
What are tumor necrosis factors?
Cytokines that promote inflammation and can cause cells to self-destruct through apoptosis
What is active immunity?
Occurs when lymphocytes are exposed to foreign antigens in the body
What is passive immunity?
- Occurs when we receive antibodies made elsewhere
- Ex: breastfeeding or placental transfers
What provides permission to a B-cell to differentiate into a plasma cell?
Helper T-cell, which was presented antigen to by an APC or a B-cell
What provides permission to an activated T-cell to differentiate into a cytotoxic T-cell?
The cytokines produced by a helper T-cell
Which cells become memory cells?
Some T and B cells
Which T-cells recognize antigens on MHC I and MHC II?
- Cytotoxic T-cell recognizes antigen bound to MHC I (CD8 x MHC 1 = 8)
- Helper T-cell recognizes antigen bound to MHC II (CD4 x MHC II = 8)
Where is MHC I present? Where is MHC II present?
- MHC I is found on all nucleated cells
- MHC II is found on APCs and B-cells
What are the three types of lymphocytes?
- B-cells
- T-cells
- NK cells
What makes up the largest portion of circulating lymphocytes?
T-cells
What are the four main types of T-cells?
- Cytotoxic
- Helper
- Suppressor
- Memory
What does antibody-mediated immunity allow?
- Enhances the innate response by opsonization
- Neutralize toxins
Which leukocyte is responsible for immunological surveillance?
NK cells
Lymphocytes that all bind to a particular antigen are called a ______.
clone
What do memory cells allow?
Stronger, more rapid response, to future antigen exposure
Which leukocytes are responsible for humoral immunity?
B-cells
Each clone of plasma cells produce a specific antigen-binding protein called an ______.
antibody
How many antigen-binding sites are there per antibody?
Two
What is IgG?
- Most common
- Secondary response is IgG
What is IgA?
- Secretory form
- Present in saliva, tears, breast milk
What is IgE?
Involved in allergic responses
What is IgM?
Antibodies involved in primary response
What is IgD?
- Found on surface of B-cells
- Role is unclear
What are the primary functions of antibodies?
- Activates B-lymphocytes
- Acts as opsonins
- Causes antigen clumping and inactivation of bacterial toxins
- Activates antibody-dependent cellular activity
- Triggers mast cell degranulation
- Activates complement
Which leukocytes are specialized to defend against intracellular pathogens?
T-lymphocytes
Which MHC class do NK cells recognize?
MHC class I
What is the reason for tissue rejection?
MHC molecules as markers of “self”
How do cytotoxic T-cells attack and destroy infected cells?
- Release perforin to create holes in infected cells
- Stimulate apoptosis (cell suicide)
What molecules serve to coordinate and reinforce innate and acquired immunity?
Cytokines
What are the immune responses to extracellular bacteria?
1) Complement
2) Phagocytes
3) Acquired immunity
4) Initiation of repair (platelets, coagulation, growth factors, cytokines)
What are the immune responses to viruses?
1) Antibodies act as opsonins
2) Macrophages present antigen to helper T-cells
3) Helper T-cells secrete cytokines to stimulate B-cells and CD8+ T-cells
4) Infected host cell displaying antigen on MHC I is killed by cytotoxic T-cells (perforin and granzyme)
What are the four types of immune hypersensitivities? Give examples.
1) Immediate (food allergies)
2) Cytotoxic (mismatched blood transfusions)
3) Immune complex-mediated
4) Delayed or cell-mediated
What is type I (immediate) hypersensitivity? Give an example.
- Localized or systemic reaction that results from the release of inflammatory molecules in response to an antigen
- Develops within seconds or minutes
- Allergies
- Antigens that stimulate it are called allergens
What is the two-step process that initiates a type I hypersensitivity?
1) Sensitization upon initial exposure to an antigen, creating memory B cells, T-cells, an antibodies
2) Degranulation of sensitized cells (mast cells and basophils)
- These steps lead to inflammation
What inflammatory molecules are released from mast cell granules? What are their functions?
- Histamine (smooth muscle contraction)
- Kinins (smooth muscle contraction)
- Proteases (activate complement)
- Leukotrienes (inflammation and smooth muscle contraction)
- Prostaglandins
What are the roles of basophils during an allergic reaction?
- Have granules that contain inflammatory chemicals
- Degranulate, like mast cells, when allergens are encountered
What are the roles of eosinophils during an allergic reaction?
- Mast cell degranulation can trigger the release of eosinophils from the bone marrow
- Eosinophils in the bloodstream can degranulate (leukotrienes)
- Increases the severity of a hypersensitivity response
What is inflammation of the skin called?
- Hives
- Urticaria
What does anaphylaxis require?
Prompt treatment with epinephrine
How are type I hypersensitivities diagnosed?
- Detection of high levels of allergen-specific immunoglobulin E
- ImmunoCAP specific IgE blood test
- Skin tests
What is immunotherapy?
- Allergy shots, which can help prevent allergic reactions
- Administration of a series of injections of dilute allergen
- Repeated every two to three years
- Not effective in treating asthma
What are treatments to type I hypersensitivities?
- Antihistamines
- Asthma: glucocorticoid, bronchodilator
- Epinephrine
What are the effects of epinephrine?
- Relaxes smooth muscle
- Reduces vascular permeability
The Rh system and hemolytic disease of a newborn is an example of which type of hypersensitivity?
Type II (cytotoxic) hypersensitivity
What causes hemolytic disease of a newborn?
- If an Rh-negative woman is carrying an Rh+ fetus, antibody immune response may be initiated against the fetal cells
- In subsequent pregnancy, the fetus may be at risk for hemolytic disease
What is the treatment for hemolytic disease of a newborn?
Anti-Rh immunoglobulin (RhoGAM)
What causes type III (immune complex-mediated) hypersensitivities?
- Caused by the formation of immune complexes
- Triggers the release of inflammatory chemicals
What are examples of type III hypersensitivity localized reactions?
- Hypersensitivity pneumonitis
- Glomerulonephritis
What are examples of type III hypersensitivity systemic reactions?
- Systemic lupus erythematosus
- Rheumatoid arthritis
What are the antibodies produced against in Grave’s disease?
TSH receptor on thyroid cells
What are the antibodies produced against in type I diabetes?
Pancreatic beta cell antigens
What are the antibodies produced against in multiple sclerosis?
Myelin of CNS neurons
What are the antibodies produced against in myasthenia gravis?
Acetylcholine receptor of motor endplate
What are the antibodies produced against in rheumatoid arthritis?
Collagen
How does the action of histamine on capillary permeability result in swelling?
- When capillary permeability increases, proteins move from plasma to interstitial fluid
- This decreases the colloid osmotic force opposing capillary filtration, and additional fluid accumulates in the interstitial space (swelling or edema)
Because antibodies are proteins, they are too large to cross cell membranes on transport proteins or through channels. How then do IgAs and other antibodies become part of external secretions such as saliva, tears and mucus?
Antibodies can be moved across cells by transcytosis or released from cells by exocytosis
Why are vaccinations ineffective if the person receiving them already has HPV of the type in the vaccine?
- HPV vaccines cause the body to create antibodies to the viral capsid proteins
- If a person already has HPV, the virus is inside the cells
- Antibodies work in extracellular compartments and cannot affect viruses inside cells
A person with AB blood type is transfused with type O RBCs. What happens and why?
- The recipient has no A or B antibodies
- Does not react to RBCs of any blood type
A person with O blood type is transfused with type A blood. What happens and why?
The recipient’s anti-A antibodies cause the agglutination of type A blood cells
Molecules that attract immune cells are called __________.
A) chemotaxins
B) interleukin-1
C) bradykinin
D) opsonins
A) chemotaxins
All of the following molecules can act as opsonins EXCEPT _______.
A) acute phase proteins
B) antibodies
C) complement
D) granzymes
D) granzymes
Which of the following statements about the internal immune response is FALSE?
A) Participating immune cells must communicate with each other to carry out an organized response.
B) Participating immune cells act alone and are usually sufficient to combat an infection.
C) The invading foreign substance must be killed or suppressed.
D) Foreign substances entering the body must be detected and identified.
B) Participating immune cells act alone and are usually sufficient to combat an infection.
