Atopic Dermatitis, Hypersensitivity Type I or IV?

[Juds]

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I was searching for atopic dermatitis and found some websites saying that this sickness is a type IV Hypersensitivity, maybe because of a late presence of T helper 1?

But, because for me it is a IgE dependent response, I think it is Type 1.

 

[AlteredScale]

I was searching for atopic dermatitis and found some websites saying that this sickness is a type IV Hypersensitivity, maybe because of a late presence of T helper 1?

But, because for me it is a IgE dependent response, I think it is Type 1.

From the literature it's not IgE mediated/dependent, meaning IgE doesn't bind to allergens which then bind to mast cells via the Fc receptor to cause a release of histamine and leukotrienes.

A large proportion of patients with AD do have higher levels of serum IgE. Where are you seeing (or for you) that it is IgE dependent?

The actual mechanism is presentation of the Ag to T-cells which is Type 4.

 

[Juds]

From the literature it's not IgE mediated/dependent, meaning IgE doesn't bind to allergens which then bind to mast cells via the Fc receptor to cause a release of histamine and leukotrienes.

A large proportion of patients with AD do have higher levels of serum IgE. Where are you seeing (or for you) that it is IgE dependent?

The actual mechanism is presentation of the Ag to T-cells which is Type 4.

Hey, thanks for the answer. I thought it was Type I because the mechanism is similar to asthma, with Thelper producing IgE that binds to antigen, and causes degranulation of mast cells.

Hypersensitivity reactions - Knowledge @ AMBOSS

A hypersensitivity reaction (HSR) is an exaggerated and/or pathological immune response to exogenous or endogenous substances. HSRs are commonly classified into four types. Type I HSRs (e.g., food ...

www.amboss.com

This website says that it is type I

But if i understood you answer, it is not IgE dependent, because it needs sensibilization first, with IgE already binded in mast cells, right?

 

[AlteredScale]

Hey, thanks for the answer. I thought it was Type I because the mechanism is similar to asthma, with Thelper producing IgE that binds to antigen, and causes degranulation of mast cells.

Hypersensitivity reactions - Knowledge @ AMBOSS

A hypersensitivity reaction (HSR) is an exaggerated and/or pathological immune response to exogenous or endogenous substances. HSRs are commonly classified into four types. Type I HSRs (e.g., food ...

www.amboss.com

This website says that it is type I

But if i understood you answer, it is not IgE dependent, because it needs sensibilization first, with IgE already binded in mast cells, right?

So on UpToDate AD in and of itself is not considered a Type 1 HS. The reason for this is because the formation of AD is usually delayed and is T-cell mediated which is not the traditional mechanism of a Type 1 HS where mast cells are primed and "introduced" to a Ag via Ab FcR.

I think the issue here is the terminology is still sort of all over the place where AD can be considered an umbrella term as certain things are considered to be more of a Type 1 vs a Type 4 HS.

Using timing of the presentation of dermatological symptoms may help and this is a good article to describe these junction points in figuring out why type of HS it is: ABC of allergies: Allergy and the skin. II—Contact and atopic eczema

Your best bet however, will be to see if UW has a clear cut explanation and just stick with that. I know time is not on your side studying for this exam.

 

[pathogeN7]

Your best bet however, will be to see if UW has a clear cut explanation and just stick with that. I know time is not on your side studying for this exam.

FWIW, Dr. Ryan on BnB explicitly said because the literature is unclear at this point, they are highly unlikely to ask you what type of HS it is.