Know what an allergy is and what causes allergic reactions.
Overreactive immune system leads to reacting to things that are not a threat (allergies, autoimmune disease)
Repeat contact with antigens called allergen
four portals of entrance for allergens
Inhalants- pollen, mold spores, formalin
Ingestant- Peanut, additives, aspirin
Injectant- Hymenopteran, insect, drug, enzyme, hormone
Contactant- heavy metal, detergent, formalin, dyes
type I allergies cellular reactions involved
Sensitization- Dendritic cell present allergen to T helper
-B cell activated to form plasma and IgE (immunoglobulin E)
-Fc on IgE bind to mast cell/basophil =primed Ig-E (memory cell)
-Basophil found in blood stream and mast cell in tissue
-No symptoms
Provocative, Subsequent exposure
-Allergen arrive again
-attaches to IgE on mast cell and trigger degranulation -release cytokines(histamine, serotonin, prostaglandin, leukotriene, bradykinin)
-Systemic distribution of mediator in blood
-Symptoms on skin, upper respiratory, GI, conjunctiva
examples of atopic diseases
rash, cough wheezing
Hay fever- Allergic rhinitis
Allergic asthma- impaired breathing and severe brochoconstriction
A topic dermatitis- eczema
Cutaneous anaphylaxis-
wheal and flare inflammatory reaction to local injection of allergen
Systemic anaphylaxis/ anaphylactic shock-
sudden respiratory and circulatory disruption
how allergies are diagnosed
•Tryptase and histamine release test: Released from mast cells and basophils during an allergic reaction. Can be done in vitro.
•Skin testing: Allergens are applied to the skin
how allergies are treated?
•Treatment block pathway to an allergic reaction
-Avoid allergens- prevent degranulation of mast cell
-Corticosteroid (plasma, no synthesized IgE)
-Cromolyn( mast cell, stop degranulation)
-Antihistamine( counter effect of cytokines, prevent effects of mediatior?)
Desensitization therapy-IgG intercept allergens before they encounter IgE
SLIT-tiny allergen under tongue
What is Desensitization therapy and SLIT?
inducing the production of IgG, which act as “blocking antibodies” which intercept allergens before they encounter IgE
tiny allergen under tongue. IgG antibodies formed instead of IgE, remove allergen before reacting with mast cell
What is type II hypersensitivities
Antibodies(IgG & IgM) bind to foreign blood, initiate the complement system, and lyse blood cells
Alloantigen
different molecules on blood transfer/organ transplant
ABO blood group
antigen markers on RBC made of glycoprotein
1 from each parent. 3 different Alleles, A, B, O
A blood has N acetylgalactosamine
B blood has D galactose
O has neither A or B antigen, so has both anti A and anti B antibody(universal doner)
AB has both A & B antigen, so it has neither a or b antibody(universal recipient)
Antisera
contain Anti A/B antibody, used to test transfusions for agglutinatinon
hemolytic disease of the newborn HDN and how to prevent
Erythroblastosis fetalis
RH factor (D antigen) + Has RH allele, must be exposed
Rh- mom is sensitized to RH+ baby.
Another RH+ baby can cause HDN
RhoGAM(anti-RH antibody) can be given to mom during each preganacy to stop sensitization, block antibody
type III hypersensitivities Immune Complex Reactions
example
when antibodies combine with soluble antigens (i.e. proteins)
•Ab/Ag stuck in basement membrane
Neutrophils come and damage tissues = immune complex reaction
Arthus reaction- acute localized response to second vaccine/ drug
Serum sickness- systemic injury by antigen-antibody complex in blood
what is Autoimmune disorder-
Occurs when T-cells and antibodies do not differentiate self/ non-self attack own antigen
How type IV allergies differ from the preceding allergies
Delayed Reactions-
•Mediated by Th1 cells rather than antibodies
•Effects are delayed, showing up 48-72 hours after 2nd contact with an antigen
•Contact dermatitis- Allergen, poison oak, processed by langerhan cell then next exposure= CD8 lymphocyte
•The Mantoux TB test reaction to dead tuberculosis cells indicates that T-cells sensitized to TB present
•Host rejection of graft:
Immune system of recipient T cell recognizes class I MHC graft as foreign release IK-2. Leads to loss of donated organ.
•Graft rejection of host
Graft versus Host Disease
bone marrow transplants, when WBCs from donated marrow recognize recipient as foreign, systematic peeling rash .
•Graft rejection is lessened using immunosuppressant drugs (for life)
•Cyclosporine
•Methotrexate
•Prednisone
four classes of grafts
•Autograft: Same person (butt to face)
•Isograft: Identical twin
•Allograft: Same species, different people
•Xenograft: Different species, animal
primary vs secondary immune deficiency
(present at birth)
(acquired after birth)
Primary B cell disorder-Primary
•One or more Ig’s are reduced or absent
•Often X-linked (more common in males)
•IgA deficiency: ~1 in 600 most common
•Agammglobulinemia: Rare, absent B cells
•Infections begin at about 6 months
Primary T cell disorder-Primary
•Usually more severe as T-cells control functions are lost as well as direct cell actions
•DiGeorge Syndrome (thymic aplasia) absent:
•Absence of thymus
•Simple disease may be fatal
•Immunizations with live microbes may not be possible
-more common in males
B and T Cell Disorders-Primary
•Severe Combined Immunodeficiencies (SCIDs)
•Lack of both stem cell lines
•Infections begin within days of birth
•E.g. Adenosine deaminase deficiency (ADA)- autosomal recessive defect in metabolism of adenosine
Secondary (Acquired)
•Infection (HIV, Epstein-Barr virus, measles virus, Hansen’s disease (leprosy)
•Organic disease (Cancer, diabetes)
•Chemotherapy
•Radiation
Serological test-
•Antibodies can be used to detect specific antigens in blood, urine, cerebrospinal fluid
Agglutination, precipitation, complement fixation, fluorescent, antibody test
difference between agglutination and precipitation
•Antibodies are used to detect soluble antigens (proteins)
•Typically only visible under a microscope
•Antibodies are used to detect cells
•Typically visible with the naked eye
Titer-
concentration of antibody in serum by diluting
Direct ELISA
Capture or antibody sandwich ELISA)
detect the presence of an antigen (bacterial cell, virus).
Well of ELISA coated with antibodies
Antigen sandwich between 2 antibody
Unbound antibody washed away
Indirect ELISA
used to detect the presence of antibodies (e.g. against Coronavirus)
•The level of antibodies in the serum is referred to as titer.
High titer=high level of antibodies
Well of ELISA coated with antigen
Antibody used to detect other antibody
Unbound antibody washed away
systemic autoimmune
antibodies against red and white blood cell
•Autoantibodies attack histone proteins within the nucleus
•Damage to kidneys, lung, heart, skin rash
•90% female
Lupus (SLE)
systemic autoimmune disease
joint lining
•Rheumatoid arthritis
specific autoimmune
•Autoantibodies and/or T cells attack the thyroid
•Graves disease and Hashimoto’s disease
specific autoimmune
•Autoantibodies and T cells damage the pancreas
Type I Diabetes
specific autoimmune
muscle weakness.
antibody against acetylcholine receptor on nerve muscle junction alter function
•Myasthenia gravis
specific autoimmune
lesions in the insulating myelin sheath that surround neurons in the white matter of central nervous system
Multiple sclerosis-
antibody react with heart valve
rheumatic fever
identify only a specific antigen
•Specificity:
identify small amounts of an antigen or antibody.
•Sensitivity:
Type I
common allergy and anaphylaxis
IgE, mast cell, basophil, allergic
Anaphylaxis, allergies, hay fever
Type II
IgG and IgM mediated cell damage cause cell lysis
blood group incompatibility, pernicious anemia, myasthenia gravis
Type III
immune complex diseases
IgG deposited into basement membrane
lupus, rheumatoid arthritis, serum sickness, rheumatic fever
Type IV
T cell mediated
delayed hypersensitivity and cytotoxic reaction
contact dermatitis, graft rejection
Atopy:
allergy that is localized to region, not life threatening. Rash asthma, coughing wheezing
•Anaphylaxis:
allergy that is systemic, airway obstruction, chemical mediator elevated. (bee stings, peanuts, injection of antibiotics)
Corticosteroid
allergy med to stop plasma, no synthesized IgE
Cromolyn
allergy med to stop mast cell, stop degranulation
Antihistamine
allergy med to stop counter effect of cytokines, prevent effects of mediatior
Same person (butt to face)
•Autograft
Identical twin
•Isograft:
Same species, different people
•Allograft:
Different species, animal
•Xenograft: