BLD434 Section 6 Flashcards
Type I hypersensitivity
- Immediate (2-30 min rxn time); Anaphylaxis
- IgE mediated, mast cell degranulation; releases mediators like histamine
- Involves mast cells, basophils, eosinophils, Th2
- Ex: asthma, hay fever, food allergy
Type II hypersensitivity
- Cell or surface bound Ab
- Cause cytotoxicity, ADCC, complement activation
- Rxn time = 5-8 hours
- Involves IgG, IgM, phagocytes
- Ex: hemolytic anemia, HDFN, Goodpasture’s Syndrome, Grave’s Disease
Type III hypersensitivity
- Immune complex mediated
- Involves complement activation
- Rxn time = 2-8 hours
- Involves IgG, phagocytes, mast cells
- Ex: Arthus reaction, Rheumatoid arthritis, Systemic Lupus Erythematosus, “serum sickness”
Type IV hypersensitivity
- Delayed (24-72 hr rxn time)
- Only cell-mediated hypersensitivity; no Ab
- Sensitized T cells, activated macrophages (redness, swelling)
- Involves Th1, Tc (CD8+), macrophages
- Ex: Contact dermatitis, Celiac disease, poison ivy
Total serum IgE testing: uses, advantages, disadvantages
- RIST (Radio-Immunosorbent Test)
- Measures the overall level of IgE ab in the blood to assess if a person has an allergic predisposition
- Pros: simple & safe
- Cons: Lacks specificity
Skin prick testing: uses, advantages, disadvantages
- Used for Type I hypersensitivity
- Pros: A positive test is clinically significant. Simple, easy, very sensitive & specific
- Cons: Danger of systemic rxn. Traumatic to patient. Test limited to individual allergens
Allergen specific testing for IgE: uses, advantages, disadvantages
- RAST (Radioallergosorbent Test)
- Pros: Can be used when patient is taking anti-histamine. Requires a single skin puncture (less traumatic). Increased sensitivity
- Cons: Lower specificity than skin testing. Only tells if IgE is present, not if it’s responsible for pt symptoms
What cells are responsible for autoimmune disease?
CD4+ T cells, CD8+ T cells, and B cells.
What two proteins are involved in T lymphocyte self-tolerance? What can happen when they are defective in humans?
AIRE (Autoimmune Regulatory Element) & FOXP3 (Forkhead box protein P3)
Defects, like deletion mutations, will lead to autoimmune disease.
Relative risk
The likelihood of those with a risk factor developing an associated disease compared to those without the risk factor (general population). But, just because one has the risk factor, doesn’t mean they will get the disease
Ex: HLA gene susceptibility
Relative risk score interpretation: 1, >1, and <1
1 = no association
>1 = positive association
<1 = negative association
Ex:
>150 means pt is 150x more likely than gen. pop. to develop the AI disease if they have the HLA associated allotype.
0.02 means pt only has 1/50 risk of developing the disease
How are HLA alleles involved in the development of autoimmunity?
HLA, MHC I, and MHC II present peptide Ag to CD4 and CD8 T cells. Then T cells lose tolerance to self-Ag (lose their ability to prevent an immune response to self-Ag). Then autoreactive T cells get activated, leading to an immune response against self-tissues.
6 Risk Factors for Autoimmune Disease Development
1) Defects in AIRE or FOXP3
2) Gender (females more often affected)
3) Environment:
Traumatic injury, Molecular mimicry, chemicals, pollutants
4) Polyclonal B cell activation
5) Inhibitory Fc gamma R polymorphisms
6) Genetic mutations in C1-C4
Molecular mimicry
An immune response to a pathogen triggers a TCR/BCR activation that cross-reacts with self-Ag
Epitope spreading
The development of an immune response to epitopes distinct from the disease-causing epitope. This gives the immune system the ability to attack multiple targets on a pathogen.
Is responsible for chronic worsening of autoimmune disease the longer the person has it.
Can be attributed to sloppy linked recognition between B and T cells.
IVIg
Intravenous immunoglobulin -
A treatment for patients who cannot make Ab due to an inherited immunodeficiency.
Currently used for Grave’s disease and immune thrombocytopenia.
RhoGAM
A medicine given to pregnant women/moms who are Rh-negative to prevent hemolytic disease of the newborn.
Polyclonal IgG is purified from pooled serum to get anti-Rh Ab. It contains Rh-positive proteins.
Monoclonal antibody preparation treatment
Recombinant protein therapies used to target and kill tumor cells or act as immunosuppressants