What is humoral immunity?
adaptive immunity where B cells secrete antibodies
most common signs and symptoms of poison ivy dermatitis are
Intense itching; Skin swelling and blisters; Skin redness
Describe the skin lesions seen in Toxicodendron Dermatitis
forearm with erythematous vesiculbollous plaques and moderate excoriation
how are antihistamines effective and ineffective in treating Toxicodendron dermatitis?
They can provide relief from pruritis but it does not resolve rash.
what type of cell responds to the haptens going through the skin?
Langerhan cells (APC -antigen presenting cell)
Define Type I hypersensitivity reaction
reaction mediated by IgE antibodies.
What can early withdrawal of steroid therapy lead to with Toxicodendron dermatitis?
recrudescence of the lesions.
What is the most common cause of contact dermatitis?
Toxicodendron dermatitis
Why is an oatmeal bath a good treatment for Toxicodendron dermatitis?
Colloidal oatmeal binds to your skin and forms a protective barrier; helps hold in moisture and ease inflammation
What caused the bullae to develop in Toxicodendron Dermatitis?
CD8 T cells caused keratinocyte apoptosis->loss cellular adhesion->spongiosis->papule->bullae/vesicle
what do CD4+ helper T cells release?
cytokines
What is the sensitization phase in allergic contact dermatitis?
Haptens penetrate epidermis->activate langerhan cells->lymph nodes->activate naive T cells
What is the elicitation phase in allergic contact dermatitis?
Re-exposure to haptens->type IV hypersensitivity reaction-> sensitized Tcells circulate to skin where antigen is
In Toxicodendron Dermatitis, does the fluid within a bullae contain urushiol?
No.
What type of hypersensitivity reaction is Toxicodendron dermatitis?
Type IV hypersensitivity
how do you diagnose toxicodendron dermatitis?
Clinically by look of skin and by HPI from patient but no need for special testing (skin test)
What is the first line of treatment with Toxicodendron dermatitis?
Washing with soap and water as soon as possible
What type of dermatitis is Toxicodendron dermatitis?
Contact Dermatitis (allergic contact)
What type of medication can suppress the immune system of someone with Toxicodendron dermatitis?
Systemic Corticosteriods
How do you prevent toxicodendron dermatitis?
Wear protective clothing, heavy gloves while gardening, washing contaminated clothes
What is cell mediated immunity?
adaptive immunity which is mediated by activated, antigen-specific T cells
Define type IV Hypersensitivity reaction
delayed cell-mediated immune reaction; involves T cells (CD4 or CD8) with antigens
Do CD4+ helper T-cells recognize MHC I or II?
MHC II
what type of immune cell kills the urushiol?
killer T cells
What do macrophages release that cause changes in the skin and what changes do we see?
proinflammatory cytokines (TNF, IL-1, IL-6) --> leaky endothelial barrier = edema + redness
General mechanism of action for an antihistamine medication
competitive antagonism of histamine binding to cellular receptors (specifically, the H1-receptors)
What do macrophages release (3 things) that cause tissue damage?
Lysosomal enzymes, Complement components, reactive species
Do CD8+ killer T-cells recognize MHC I or II?
MHC I
General mechanism of action for a corticosteroids
downregulate expression of inflammatory cytokines, reduce activity immune system
Describe an urticarial lesion
wheals/hives - migratory, elevated, pruritic, reddish plaques caused by local dermal edema.
Define Type II hypersensitivity reaction
cytotoxic reaction mediated by IgG or IgM antibodies
Describe basic structural components of an antibody
Light chain, heavy chain, variable region, constant region
what is the offending allergen in Toxicodendron?
Urushiol oil
Small and large blisters (vesicles and bullae) from Toxicodendron dermatitis are prone to what complication?
Such lesions are prone to bacterial superinfection, which produces a yellow crust (impetiginization).
What is a hapten?
low molecular weight antigen
About how many hours does it usually take to develop an itchy rash from urushiol oil?
24-48 hours (delayed response)
Define Type III hypersensitivity reaction
reaction mediated by immune complexes