The Skin you're in.

Hi everyone, I hope your finals went well.

I have for some time, been fascinated by the largest organ of our bodies, the skin. When I was talking with a friend of mine last week about studying for my Immunology final allergies came up and I found out something I never knew about her. I've seen her drink margaritas on more than one occasion, and so I saw surprised when she told me that she's allergic to limes. Upon further explanation she told me she can eat limes fine with no problem, but if she gets lime juice on her skin and it's exposed to sun light, her skin turns purple. My reaction... cool!

Looking further into it I found that is condition is called Phytophotodermatitis, unfortunately a non-immunological based response. But It got me thinking about people that do have allergies to sunlight, photosensitivity, and how the process works.

There are a lot of different types of photsensitivity I've found out. One in particular polymorphous light eruption (PLE) is very common and is a Type IV hypersensitivity. When our skin is exposed to UV, there is a normal increase in IL-4 neutrophils. These intern produce IL-10 and recruit Th2 cells which then go on to call in the M2 macrophages, which from class we found out are key recruiters in M2 Macrophages which help in clean up and repair. With PLE there is something blocking and or reducing this process that isn't entirely understood, although mast cells as well as Treg cells have be looked at as possible culprits because of there suppressive abilities. 

 

To the right is a diagram that helps lay out normal vs. PLE skin reactions to UVB from Wolf, Byrne and Gruber-Wackernagel 2009. 

Does anyone know of other interesting dermatology-immunology reactions that are out there? I had thought I found another one, but it turned out to be chemically related, not immunological,

Wolf P, Byrne S.N, Gruber-Wackernagel A. 2009 New insights into the mechanisms of polymorphic light eruption:resistance to ultraviolet radiation-induced immune suppression as an aetiological factor. Exp Dermatol. 18: 350-356.