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78 Cards in this Set
- Front
- Back
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What is an allergy? |
The altered, usually exaggerated, immune response to an allergen. sometimes used interchangeably with hypersensitivity. |
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What causes allergic reactions? |
When the immune system becomes "sensitized" to an other harmless particle, it overreacts in a variety of ways. |
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What are the main categories of immunopathology and their medical consequences? |
Overactivity - allergic reactions, autosensitivity Underactivity- immunocompromisation, genetic disorders |
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What are the 4 types of allergies? |
Type I (common allergies and anaphylaxis) Type II (IgG and IgM mediated cell damage) Type III (B-cell Ig responses) Type IV ( delayed hypersensitivity/T cell responses) |
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What are the 4 portals of entrance for an allergen? |
Inhalation Ingestions Injection Contact |
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What are the cellular reactions involved in an allergic response? |
An allergy first develops with the sensitizing dose, where the allergen enters through a mucous membrane and is picked up by a dendritic cell and presented to a T helper cell. The B cell activated by the T cell reacts and forms a plasma cell, which synthesizes IgE specific to the allergen Then, when the person is exposed to the allergen again, it is immediately detected and goes directly to primed mast cells with specific receptors. This triggers degranulation which releases chemical mediators into the bloodstream |
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What cells are key role players in an allergic reaction |
Mast cells primed with IgE Basophils primed with IgE B cells T cells APCs |
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What are the primary chemical mediators of an allergic reaction? |
Histamine serotonin leukotriene prostoglandins bradykinin |
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What muscles do chemical mediators tend to react with? |
Smooth muscle such as glands, muscles surrounding blood vessels and bronchi |
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What is the difference between atopic allergies and anaphylactic allergies? |
Atopy is mild, causes rashes, asthma, coughing, sneezing Anaphylaxis is serious, bronchioles restrict, swelling that affects the ability to breathe |
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What types of symptoms does Prostoglandin cause in an allergic reaction? |
Dialates blood vessels Constricts bronchioles Affects nerves (headache) |
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What types of symptoms does Leukotriene cause? |
Bronchial constriction Airway obstruction |
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What sorts of symptoms do Histamine, Seratonin, and Bradykinin cause? |
Excessive mucus, tear formation, secretions Peristalsis of intestine: vomiting/diarrhea Constricted bronchiols Dialated blood vessels Increased blood flow in skin causing wheal and flare |
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What types of atopic allergies are there? |
Hay Fever Allergic asthma Atopic dermatitis |
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What types of anaphylaxis is there? |
Cutaneous anaphylaxis - wheal and flare reaction to the local injection Systemic anaphylaxis - sudden respiratory and circulatory disruption (fatal in minutes) |
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Define anaphylaxis |
An exaggerated systemic allergic reaction to antigen that leads to severe respiratory and cardiac complications. |
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What are the symptoms of an anaphylactic reaction? |
Throat swells respiration compromised blood pressure drops heart may stop |
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What is the physiological/chemical difference in an atopic vs. anaphylactic reaction? |
There is no physiological difference, however, the concentration of chemical mediators and strength of response is greatly amplified in an anaphylactic reaction. |
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How are allergies diagnosed? |
BLOOD TESTS Tryptase testing - tryptase is an enzyme released by mast cells, and it's level can indicate an allergic response. Differential blood count- indicates the levels of basophils and eosinophiles, if it's elevated this indicates allergies. Leukocyte histamine-release test - measures the amount of histamine released from patients basophils when exposed to specific allergens Serological tests that use radioimmune assays that reveal quantity and type of IgE SKIN TEST Patients skin is pricked/injected/scratched with a pure allergen. Doesn't work for most food allergies. 20 minutes and skin is appraised for redness and elevation |
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How are allergies treated? |
Avoiding the allergen Taking drugs that block the action of lymphocytes, mast cells, or chemical mediators Undergoing allergen desensitization |
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Antihistamines, aspirin, epinephrine, theophyline counteract: |
the effects of cytokines on smooth muscle and membranes |
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Cromolyn acts on: |
the surface of the mast cell, prevents degranualtion |
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Monocolonal drugs: |
inactivate IgE |
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Corticosteroids: |
keep plasma cells from synthesizing IgE and inhibit T cells |
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How do anithistamines work? |
They bind to histamine receptors in target organs, preventing histamine from binding. |
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What is desensitization/hyposensitization? |
A therapeutic exposure to known allergens designed to build tolerance and eventually prevent allergic reaction. Hyposensitization is gaining in use because it emphasizes that the allergy is reduced not completely removed. |
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What are the theroies regarding how hyposensitization works? |
Injected allergens stimulate the formation of allergen specific IgG, instead of IgE. These IgG antibodies remove allergens from the system before is can bind to IgE, preventing degranulation. Or, the allergen itself binds directly with IgE and is removed from circulation before it can react with mast cells |
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What is a Type II hypersensitivity? |
complex group of syndromes that involve complement-assisted destruction of cells by antibodies. |
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What types of type II hypersensitivitites are there? |
<transfusion reactions> some autoimmunities (immune system attacking self) |
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What are ABO markers? |
They are markers on a blood cell. They are inherited from both parents: AB are dominant over the recessive O, and codiminant with one another. |
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Describe the antibodies in serum that are related to blood. |
These antibodies are pre-made, and exist even if contact with the other blood type has never occured. A blood types will have anti-B antibodies, and B blood types will have anti-A antibodies. Type O blood will not react to either. |
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What are the clinical implications of ABO/rH reactions? |
Types must be matched at all times, or an immediate and deadly reaction will occur. |
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Which blood type is the universal donor? |
O |
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Which blood type is the universal recepient? |
AB |
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What happens during a transfusion reaction? |
massive hemolysis and complement cascade which leads to systemic shock and kidney failure due to the blockage of glomeruli (blood filters) by cell debris. RBC destruction can also cause fever, anemia, and jaundice. |
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What is an Rh factor? |
An isoantigen that can trigger hemolytic disease in newborns due to incompatibility between maternal and infant blood factors. |
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Explain hemolytic disease and how rH incompatibility relates to it. |
Hemolytic disease of the newborn occurs in an Rh+ fetus whose mother is Rh-. Hemolytic disease does not occur for the first child with a + Rh factor, as this is when sensitivity to the + Rh factor is being built. With the second child, fetal blood escapes into maternal circulation and illicites a memory response, which causes anti-Rh anitbodies to cross the placenta into fetal cirulation. These maternal anti-Rh antibodies affix to fetal RBCs and cause complement mediated lysis. |
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How is erythroblastosis fetalis prevented? |
Immunizations with an antiserum containing antibodies against the Rh factor, preventing the mother from becoming sensitized. |
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How are the hypersensitivities derived against A or B blood if there has never been any contact? |
They develop in infancy through exposure to certain antigens that are widely distributed in nature. These antigens mimic A and B antigens and stimulate the production of antibodies that cause reactions. |
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What are the antigens on blood made up of? |
They are made out of terminal sugars and a "common" portion. |
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What is a type II hypersensitivity? |
group of syndroms that involve complement assisted destruction of cells by antibodies directed aginst those cells' surface antigens |
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How is type III different than a type II reaction? |
They are similar, but type III reacts to antigens that are not attached to the surfaces of cells. These reactions produce free-floating complexes that can be deposited in tissues. |
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Define an immune complex reaction |
Type III hypersensitivity of the immune system. It is characterized by the reaction of soluble antigen with antibody, and the deposition of the resulting complexes in basement membranes of epithelial tissue. |
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Define basement membranes |
A thin layer (1–6 μm) of protein and polysaccharide found at the base of epithelial tissues. |
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How does a type III reaction occur? |
Antibody combines with a soluable antigen, forming Ag-Ab complexes These complexes lodge in basement membranes of epithelia in blood vessels, kidney, skin, and other sites. Complement factors trigger the release of inflammatory mediators Neutrophiles release enzymes and chemokines that damage target tissues and organs. |
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What are two examples of type III hypersensitivities? |
Arthus Reaction - acute response to 2nd injection of a vaccine or drug. Mainly due to destruction of tissues in and around blood vessels and the release of histamines from mast cells and basophils. Normally self limiting, rapidly clears. Can cause blood clotting which can occasionally cause necrosis and loss of tissue. Serum Sickness- caused by injections of animal hormones and drugs. The immune complezes enter circulation and are eventually deposited in blood vessels, kidneys, heart, skin, and joints. Can be chronic, causes enlarged lymph nodes, rashes, painful joints, swelling, fever, and renal dysfunction. |
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What characteristics set serum sickness and the arthas reaction apart from anaphylaxis? |
They depend upon IgG, IgM, or IgA rather than IgE Require large doses of the antigen Symptoms are delayed by hours or days |
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Is the arthus reaction localized or systemic? |
localized |
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Is the serum sickness localized or systemic? |
Systemic |
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What is a type IV hypersensitivity? |
Also known as delayed hypersensitivity, symptoms arise one to several days following the second contact with an antigen. |
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How, in general, do type IV hypersensitivities occur? |
They result when T cells respon to antigens displayed on self tissues or transplanted foreign cells. |
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What are some examples of type IV hypersensitivity? |
allergic reactions to infectious agents contact dermatitis graft rejection |
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What is an example of contact dermatitis? |
Poison Ivy |
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What is an example of hypersensitivity caused by an infection? |
A TB test which is an extract of the bacterium Mycobacterium tuberculosis. INjected under the skin, if previous contact has occured with it, it will cause a reaction at the injection site. |
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What are the four types of grafts? |
Autograft Isograft Allograft Xenograft |
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How does host rejection of the graft occur? |
T cells of the host recognize foreign MHC I markers on the graft. They release cytokines that create more helper and cytotoxic T cells that react to the MHC I marker on the graft. Cytotoxic T cells bind to the grafted tissue and secrete lymphokines that begin the rejection process, which ends with the destruction of the vasuclar supply to the graft, promoting the death of the tissue or organ. |
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How does graft rejection of the host occur? |
Most common in bone marrow transplants, these grafts have an indigenous population called passenger lymphocytes. These lymphocytes are mobillized within the circulation/lymph system and attack the hosts MHC I markers. Papular peeling skin rash is most common symptom, other organs affected are liver, intestine, muscles, and mucuous membranes. |
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How is a bone marrow transplant done? |
Bone marrow aspirated from donor Recipient is treated with chemo and whole body irradiation to destroy their own blood stem cells and prevent rejection of new cells. Harvested bone marrow is dripped intraveinously where marrow cells settle into appropriate regions. |
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How can stem cells be harvested directly from the blood? |
Leukapheresis is used to separate the stem cells from the blood, and flow symmetry is used to identify and collect them. |
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What is primary autoimmune disease? |
Present at birth stems from genetic errors |
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What is secondary autoimmune disease? |
Aquired after birth Cuased by natural or artificial agents |
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What are some examples of primary autoimmune disease? |
DiGeorge syndrome |
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Explain the sequestered antigen theory |
Some tissues are immunologically "protected" behind anatomical barriers and cannot be surveyed by the immune system (CNS, eye lens, antigens in thyroid and testes). Over time these protected areas can become exposed to the immune system by infection, trauma or deterioration, and can be percieved by the immune system as a foreign substance (antigen) |
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Describe forbidden clones and how they can cause an autoimmune reaction |
The immune system of a fetus develops tolerance to self by eradicating self reacting lymphocytes called forbidden clones. If these clones survive, they can attack tissues carrying MHC I markers, which they mistake as antigens |
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Describe the theory of immune deficiency |
Mutations in the receptor genes of some lymphocytes make them reactive to self T regulatory cells that normally maintin tolerance to self can become dysfunctional |
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Describe molecular mimicry |
When a microbial antigen bears molecular determinants similar to normal human cells. An infection with this type of microbe can cause antibodies to be developed that cross-react with tissues. |
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How is viral infection related to autoimmunity? |
A viral infection is suspected to trigger type I diabetes and MS. Viruses can noticeably alter cell receptors, causing immmune cells to attack tissues bearing viral receptors. |
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What are some examples of systemic autoimmunities? |
Rheumatoid arthritis Lupus |
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What are some examples of specific automimmunities? |
Graves disease Hashimotos thyroiditis Diabetes Type I MS |
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What type of hypersensitivity is MS? |
II and IV |
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What type of hypersensitivity is RA? |
III and IV |
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what type of hypersensitivity is Lupus? |
II and III |
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Explain DiGeorge symdrome. Why is it so serious? |
DIgeorge syndrome invovles an underdevelope thymus gland along with other physical deformities. Becuase the thymus gland is inactive, T cells cannot activate B cells and no antibodies can be prodouced. |
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What is agammaglobulinemia? |
The absence of Ig, period. This disease starts with recurrent, serious infections, treatments include immunotherapy with serume globulin and continuous antibiotics |
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What is a severe combined immunodeficiency? |
A collection of syndromes occurring in newborns caused by a genetic defect that knocks out both B-and T-cell types of immunity. There are several versions of this disease, termed SCIDS for short. |
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Name an example of a SCID |
Adenosine deaminase deficiency, which is cuased by an autosomal recessive defect in the metabolisim of adenosine. LYmphocytes develop, but a metabolic product builds up to abnormal levels and destroys the cells. |
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How are secondary immunodeficiency diseases caused? |
infection organic disease chemotherapy radiation |
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Which infections can cause secondary immune deficiency disease? |
HIV Epstein Barr Measles Leprosy |
