Short-term and long-term UVB-induced immunosuppression in human skin exhibit different ultrastructural features.

Short-term ultraviolet B light (UVB)-induced immune suppression was established by the ability of UVB to inhibit induction of allergic contact dermatitis (ACD) to dinitrochlorobenzene (DNCB). The long-term effect was assessed by a dramatic reduction of the mixed-epidermal cell lymphocyte reaction (MECLR) responses. Immuno electron microscopic (IEM) investigation of HLA class II localization on epidermal Langerhans cells (LC) (pivotal for the immune response of the skin) showed no difference in HLA class II expression after UVB-exposure compared to control skin, both after short-term and long-term UVB-exposure. Ultrastructural examination of the epidermis revealed a normal appearance of the epidermal cells after long-term UVB-exposure. However, after short-term UVB-exposure the epidermis exhibited many abnormalities, ranging from the stratum corneum to the basal membrane. So although both short- and long-term UVB exposures were able to cause immune suppression in the skin, those processes were not accompanied with identical morphological epidermal features.