Reversal by lymphokines of the age-related hyporesponsiveness to contact sensitization and reduced Ia expression on Langerhans cells.

Contact sensitivity responses were evaluated in young adult (3-5 months) and aged (16-26 months) BALB/c mice which were systemically treated with interleukin-2 (IL-2), interferon-gamma (IFN-gamma) or saline. Mice older than 16 months of age have deficient numbers of Ia+ Langerhans cells in addition to their well-known impaired T cell functions. They also have an impaired cell-mediated response to contact sensitization with 1-chloro-2,4,6-trinitrobenzene. This hyporesponsiveness in aged mice can be almost completely reversed by IL-2 and is marginally improved by IFN-gamma. Exposure of skin from aged mice to interleukin-2 or interferon-gamma, both in vivo and in vitro, causes increases in the density of Ia+ Langerhans cells to levels approximating those in young mice. Since IFN-gamma causes partial restitution while IL-2 fully restores the contact hypersensitivity in aged animals, we conclude that the hyporesponsiveness in aged mice results both from defective Ia antigen expression on the antigen-presenting Langerhans cells and from deficient T cell function.