Enhancement by various cytokines or 2-β-mercaptoethanol of Ia antigen expression on Langerhans cells in skin from normal aged and young mice. Effect of cyclosporine A

The number of Ia⁺ Langerhans cells (LC) in skin from aged (16- to 18-mo-old) BALB/c mice is approximately 40% lower than in skin from young (2- to 3-mo old) mice. Overnight incubation at 37°C with a variety of cytokines, including IL-1, IL-2, IL-3, IL-4, IL-6, TNF-α, IFN-γ, and granulocyte/macrophage-CSF, causes a significant increase in the Ia expression on LC and raises the number of Ia⁺ cells by at least 300/mm² in skin from both young and old mice. At 1 to 5 x 10^-5 M, 2-ME has a similar effect. The percentage increment in Ia⁺ cells is much higher for skin from aged mice than from young mice, particularly with IL-3, which appears to reconstitute the number of Ia⁺ LC in skin from aged mice to that of IL-3 exposed skin from young mice. Under the incubation conditions of our experiments, neither keratinocytes nor Thy-1⁺ dendritic cells acquire Ia Ag. Addition of 10 μg/ml cyclosporine A to the medium abolishes the effect of 2-ME and of all of the cytokines except IL-2 and IL-6. These results demonstrate the presence of a significant population of Ia^- LC in the epidermis of both young and aged mice. It is suggested that epidermal production of cytokines may be of importance in the maintenance of constitutive Ia expression on LC. The possible interaction between keratinocytes and LC and the effect of aging on this process are discussed.