The alternative complement component factor B regulates UV-induced oedema, systemic suppression of contact and delayed hypersensitivity, and mast cell infiltration into the skin.

Ultraviolet (UV) wavelengths in sunlight are the prime cause of skin cancer in humans with both the UVA and UVB wavebands making a contribution to photocarcinogenesis. UV has many different biological effects on the skin that contribute to carcinogenesis, including suppression of adaptive immunity, sunburn and altering the migration of mast cells into and away from irradiated skin. Many molecular mechanisms have been identified as contributing to skin responses to UV.