Diminished immune response in sun-damaged skin.

In previously sensitized volunteers, higher concentrations of 2,4-dinitrochlorobenzene were necessary to elicit positive patch test reactions on the sun-damaged skin of the neck than on the protected skin of the upper part of the back. This difference was not found in subjects without evidence of sun damage, and there was no difference between sun-damaged and nondamaged skin in response to a primary irritant. Responses to intradermally injected common antigens were also less intense in sun-damaged skin that in nonexposed skin. These findings suggest the existence of a local defect in cell-mediated immunity in skin altered by long-term sun exposure.