3 - Immune Physiology 2 Flashcards
Acquired immunity consists of _____ and _____
lymphocytes and antibodies
What’s the difference between an antigen and an immunogen?
Antigen refers to any molecule that can react with binding sites on antibodies or antigen receptors
Immunogens are antigens that WILL induce an immune response
All immunogens are antigens, but not all antigens are immunogens
What are haptens?
Antigens that are too small to be immunogenic until they bind with a larger carrier molecule
PCN and poison ivy have haptens. they initiate allergic response only after binding to large proteins in the blood or skin
What is an allergen?
An antigen that produces an allergic response
Antigens are directly recognized by three molecules:
circulating antibodies
Antigen receptors on B lymphocytes
Antigen receptors on T lymphocytes
Which immunoglobulin crosses the placenta?
IgG
IgG, IgM, IgA etc are all examples of _______
Which are produced by _____
Which are descended from ____
antibodies
plasma cells
B-cells
Due to the prevalence of transplant studies, Major Histocompatibility Complexes (MHCs) are often referred to as:
Human leukocyte antigen (HLA)
What are the three “Professional” APCs?
Dendritic Cells
Macrophages
B Lymphocytes
If you’re exposed to a pathogen you’ve never encountered, which antibodies will be most prevalent during the response?
What about if you’re exposed to something you’ve been immunized against or had before?
Pretty much equal amounts of IgG and IgM
Way more IgG
What are the direct effects of antibodies when they encounter antigens?
- Neutralization
- Agglutination
- Precipitation
How do antibodies cause neutralization
cover sites on the microorganism that would normally attach to the body’s cells, preventing attachment to the host
Molecularly, most toxins are:
proteins that bind to surface molecules on cells and damage those cells
What are the indirect actions of antibodies?
Activation of complement and phagocytes
What are monoclonal antibodies?
Usually pathogens have several antigenic determinants, which form different antibodies - so there are several antibodies for one pathogen. In the lab, only the antibody that is most effective or protective is cloned,
Hence monoclonal
_____ is the dominant secretory immunoglobulin
IgA
Type 1 hypersensitivity reactions are mediated by:
IgE and the products of tissue mast cells
Most common allergies are Type _____ reactions
1
Histamine acting on an H1 receptor causes:
bronchial constriction
increased vascular permeability
vasodilation
Histamine acting on an H2 receptor causes:
increased gastric acid secretion
decreased histamine release from mast cells and basophils
Type II hypersensitivity reactions are ______ reactions
Tissue Specific
Think HLA
Grave’s Disease is an example of a ______ hypersensitivity reaction
Type II Tissue
autoantibody binds to and activates receptors for TSH, stimulating the thyroid to produce more thyroxine
Name the mediators for the each hypersensitivity
I - IgE
II - Tissue Specific (HLA)
III - Immune Complex
IV - Cell-mediated
Most type III hypersensitivities are caused by:
antigen-antibody complexes formed in the circulation and deposited in vessel walls or tissues
Type II and Type III hypersensitivity reactions both involve antibodies binding to antigens on tissues, so what’s the difference?
In Type II reactions, the antibody binds directly to the cell membrane of the tissue
In Type III, the antibody binds to soluble circulating antigens, which then gets deposited in a tissue
Type III reactions are organ specific. The antibody isn’t targeting that tissue. It’s just winding up there d/t circulation etc
The harmful effects of immune complex deposition are caused by:
complement activation, which are chemotactic for neutrophils
neutrophils bind to the complexes and try to ingest them
Why is it problematic for neutrophils to attack immune complexes that are deposited in tissues? Shouldn’t that be helpful?
Neutrophils have a hard time because the complexes are bound to large areas of tissues
While they’re trying to digest the complexes, they release tons of lysosomal enzymes directly into the tissue site - directly, not through phagolysosomes
this attracts even more neutrophils and more enzyme release which leads to tissue damage
Immune complexes can be big, medium, or little. What happens to the different sizes?
Big ones are usually cleared rapidly by macrophages
the little ones are cleared by the kidneys without difficulty
its the medium sized ones that are problematic
Describe the effect of each hypersensitivity type on circulating complement level
Type I, II, and IV: no change
Type III: decreased (consumptive)
Type III hypersensitivity reactions can be systemic or localized. What are the names for these?
Systemic: Serum Sickness
Localized: Arthus reaction
What is an example of a serum sickness?
Raynaud Phenomenon
Caused by immune complexes that precipitate at temperatures less than body temp
Predominantly precipitate in colder areas: fingers, toes, nose, ears
What are the tissues most effected by serum sickness?
vessels, joints, kidneys
Types I, II, and III hypersensitivities involved antibodies. Type IV involve _____
T cells
Do not involve antibodies
The TB skin test is an example of which hypersensitivity reaction?
Type IV
What are some clinical examples of Type IV hypersensitivity?
Graft Rejection
Allergic reactions from poison ivy and metals
Allergens that induce type I hypersensitivities include:
Pretty much anything environmental:
pollen, mold, fungi
foods
animal dander
cigarettes, dust etc. etc.
Allergens that induce Type IV reactions include:
plant resins
metals
rubber/cosmetic/detergent chemicals
Topical antibiotics
Which hypersensitivity reaction types are relatively rare?
Type II and III
Usually d/t ABX or infectious diseases (hep B)
In families in which one parent has an allergy, _____% of offspring will have that allergy
40
If both parents have an allergy, ____% of offspring will have that allergy
80
People who are genetically predisposed to develop allergies are called _____
atopic
Why are atopic individuals so much more likely to develop allergies?
They tend to produce higher levels of IgE and have more Fc receptors on their IgE mast cells
Bee venom is a type ____ reaction
1
Why does gradually giving more and more of a drug allow sensitization?
It develops IgG antibodies, which compete with the IgE antibodies and effectively neutralize the substance before IgE can bind with it
Type II and III reactions are mediated by _____
IgG and/or IgM
Central tolerance is developed in:
Peripheral tolerance is maintained in:
the embryonic period
the secondary lymphoid organ (thymus, bone marrow)
Autoimmune disease results from a breakdown in ____ tolerance
peripheral
There are 6 ways peripheral tolerance can break down:
- Lymphocytes leak into what should be a sequestered area and encounter “foreign” tissues
- Molecular mimicry d/t an infectious disease
- Neoantigens formed by haptens binding to self proteins
- Survival of an auto-reactive clone that didn’t get weeded out in the thymus
- Defective regulation of clones by secondary lymphoid organs
- A silent imitator
When one eye is traumatically injured, why is the other often injured by the immune system?
What is this an example of?
Lymphocytes are exposed to areas of the eye that are usually non-accessible, and develop antibodies to those tissues
The circulating antibodies attack the other eye
Example of sequestered antigen causing autoimmune disease
In SLE, the most common autoantibodies produced are against ______
nucleic acids, histones, and other nuclear materials
Why is SLE so likely to cause kidney damage?
The circulating DNA-containing immune complexes have a very high affinity for the basement membrane of the glomerulus.
They are selectively deposited in the glomerulus
Which two drugs, when taken for prolonged lengths of time, can cause SLE-esque syndromes?
Hydralazine
Procainamide
What is the most severe primary immune deficiency?
Severe combined immune deficiency
What causes severe combined immune deficiency (SCID)?
A common stem cell for all WBCs is absent, there is no development of T cells, B cells, or phagocytes at all
Why are encapsulated bacteria likely to cause infection when there are altered levels of antibodies or phagocytes?
Because they require osponization by antibodies in order to be phagocytized
Chronic Granulomatous Disease causes a deficiency in the creation of hydrogen peroxide from NADPH, so why is it a problem for the immune system?
Because phagocytes aren’t able to produce hydrogen peroxide, and therefore aren’t able to adequately phagocytize
Why is zinc intake related to immunity?
Cofactor for lots of enzymes, some of which are found in lymphocytes
Zinc deficiency is usually caused by:
The usual things:
malabsorptive syndromes
renal failure
chronic diarrhea
burns or severe psoriasis
Diabetes suppresses the immune system by messing with:
phagocytosis
chemotaxis
lymphocyte proliferation
A splenectomy would result in decreased _____ antibodies and decreased ______
IgM response
opsonins - therefore have difficulty with encapsulated bacteria
