Dextran Alters Induction of Cell-Mediated Hypersensitivity

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Abstract
Administering dextran to 6- to 8-week-old CBA/J mice just before applying the initial sensitizing dose of a hapten caused induction of heightened delayed-type responsivity to the hapten. Measured by an isotope localization method, the cell-mediated hypersensitivity engendered by a hapten, picryl chloride, was twice as great in animals receiving dextran than in control animals given the saline vehicle. Optimal enhancement was achieved when dextran administration preceded hapten by 2 hr. Furthermore, the augmentation was observed at the first test after the initial sensitization period but not after repetitive dermal applications of the hapten had been made over a prolonged time interval. In the latter instance diminution of sensitivity was observed. Washed lymphoid cells, taken from animals 2 hr after treatment with dextran, transferred to x-irradiated syngeneic recipient animals the heightened capacity to become sensitized. Such lymphoid cells retained the ability to transfer the heightened capacity to become sensitized despite removal of macrophages by plastic-adherence. Although dextran is known to cause murine T cells to release factors that increase responses of other T cells to mitogens, it is not known whether dextran affects that subpopulation of T cells directly mediating contact sensitivity or whether its action is upon a separate subpopulation of T cells concerned with immuno-regulation.

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