Here is a link to a discussion on the FDA website about UV radiation and some of the diseases it treats:
FDA info on phototherapy (mentions Lupus)
While it doesn’t discuss UVA1 specifically, it DOES discuss the different wavelengths and a little about how they work. This piece discusses the effect UV radiation has on the body (different wavelengths do different things), how where you live matters, the health benefits (and some drawbacks for certain wavelengths) and a little about the UV spectrum. It also lists some of the diseases that have shown to benefit from using phototherapy, including Lupus.

