Skin and the Immune System Flashcards
The cutaneous immune system is composed of the […] and the […]
Epidermis and dermis
What is the role of keratinocytes in immune function of the skin?
- They provide a permeability barrier at the stratum lucidum/granulosum layer
- They produce defensins (insert into microbial membranes) and cathelicidins (direct toxicity to microbes)
- Expression of PRRs (TLRs and NLRs) that can stimulate an innate immune response
Langerhans cells
- Found in what layer of the skin?
- When do they develop?
- What type of cell are they?
- Epidermis –> Stratum spinosum
- Early in fetal development
- Specialized dendritic cell / macrophage
Dermal dendritic cells are derived from […] progenitors
Bone marrow myeloid
What do langerhans cells and dermal dendritic cells have in common?
- They both express TLRs
- Both migrate to lymph nodes to stimulate immune response
What immune cells are present in the epidermis?
Keratinocytes and langerhans cells
What immune cells are present in the dermis?
Dendritic cells
Resident macrophages
Mast cells
Mast cells
- What cells do these arise from?
- What receptor do they express?
- What do they contain in their cytoplasm?
- Bone marrow myeloid cells
- Receptor for IgE
- Granules with histamine and inflammatory mediators
Type 1 hypersensitivity is also called […] and is activated by […] cells
Immediate type hypersensitivity
Mast
Describe the process of type 1 hypersensitivity.
What are the 2 phases of type 1 hypersensitivity (allergy) response upon repeat exposure to allergen?
What cells are responsible for causing the allergic reaction seen with type 1 hypersensitivity?
Mast cells
- Resident in tissue, numerous in connective tissue under epithelia
- Release histamine, cytokines, enzymes
Basophils
- Migrate from blood
- Express IgE receptors
- Release histamines, cytokines, enzymes
Eosinophils
- Migrate from blood
- Release toxic microbial substances
What is the name for the classic dermatologic finding of type 1 hypersensitivity?
Urticaria (aka hives)
What is urticaria?
What 2 dermatologic features are characteristic of this condition?
What is atopy?
The genetic predisposition to produce IgE in response to allergen. These individuals have higher serum IgE and more Th2 CD4+ cells than general population. It is unclear why.
People who develop allergy typically have family members with allergy.
True/false
True
What role does the environment play in allergy development?
- Allergies are more common in developed countries
- Hygiene hypothesis - early life exposures to infection and mcirobes decreases likelihood of allergic response later to non-pathogenic subtances like pollen
Another name for type 2 hypersensitivity is […]
Antibody-mediated
Type 2 hypersensitivity is a diseas caused by […] against […]
Antibodies
Self
How can antibodies become self reactive?
Antibodies may be specific for normal cell antigens or foreign antigens that look very similar to self antigens, so the antibodies that are supposed to recognize foreign antigen can actually recognize self via “cross reaction”
What are the 3 main mechanisms of antibody-mediated injury in type 2 hypersensitivity?
Inflammation
Opsonization and phagocytosis / complement activation
Cellular dysfunction (antibodies directed against cell surface receptors impair or dysregulate function without causing cell injury or inflammation)
Pemphigus Vulgaris
- This is an example of what type of hypersensitivity reaction?
- What type of condition is this?
- What is that pathophysiology?
- What is the clinical presentation?
NOTE: for question 2 - Autoimmune disease of skin due to presence of IgG against desmogleins which are part of desmosomes (not tight junctions) in keratinocytes
Another name for type 3 hypersensitivity is […]
Immune complex
Describe the mechanism of hypersensitivity in type 3 hypersensitivity.
Antibodies bind to antigen (can be foreign or self antigen) and travel systemically where they tend to deposit at sites of high pressure and elicity injury at this distant site.
What causes injury in type 3 hypersensitivity?
Mechanisms of injury are similar to type 2, just at a site that is distant from where antigen originated from.
Cutaneous Polyarthritis Nodosum
- What type of hypersensitivity is this?
- This is a type of what condition?
- What features are seen in histological sections from patients with this disease?
- What are the mechanisms of injury?
- What other 2 things is this condition is associated with?
- Type 3
- Medium vessel vasculitis
- Deposition of C3 and Ig in vessel walls
- Vessel inflammation (vasculitis) and vessel injury; tender subcutaneous nodules; fever; arthralgia; myalgia
- Certain meds (antibiotics, birth control) and infections (HBV, Group A Strep)
Another name for type 4 sensitivity is […]
T-cell mediated, Delayed Type
What is the mechanism of hypersensitivity for type 4?
Contact dermatitis
- What type of hypersensitivity is this?
- In my own life, I’ve experienced this when I was bitten by bed bugs. What caused me to have the reaction that I did?
- Type 4
- Proteins in the bed bug saliva penetrated my skin and were taken up by APCs in my skin. These APCs then activated CD4+ T-cells to become Th1 cells which then traveled to the area of the bite in the skin. Here the Th1 cells released INF gamma which produced inflammation. Mast cells were also stimulated to release granules causing itching and redness. CD8+ cells also could have induced cell death as seen with the blistering skin lesions I had.
