Assessment of the Functional Activity of Antigen-bearing Dendritic Cells Isolated from the Lymph Nodes of Contact-sensitized Mice

The immunostimulatory properties of dendritic cells (DC) which rapidly accumulate within the draining lymph nodes of mice topically exposed to contact allergens have been assessed as a function of their ability to initiate proliferative responses by sensitized lymph node cells (LNC) in vitro. A proportion of such DC bear antigen which is in a highly immunogenic form. Thus, at low stimulator:responder ratios, DC-enriched populations prepared from the draining nodes of mice exposed to the skin-sensitizing fluorochrome fluorescein isothiocyanate (FITC) induced significant proliferative responses by FITC-primed responder lymphocytes. Under the same experimental conditions, unfractionated or DC-enriched LNC isolated from naive mice and coated with at least equivalent amounts of FITC in vitro were without effect. The influence of DC populations on lymphocyte proliferation was largely, but not wholly, antigen-specific in nature. Dendritic cell fractions isolated 18 h following topical exposure to high concentrations of FITC or oxazolone induced a marked proliferative response by lymphocytes sensitized to the homologous chemical and a significantly less vigorous response by lymphocytes primed to unrelated haptens. In contrast DC isolated from the nodes of mice sensitized with 2,4-dinitrochlorobenzene (DNCB) caused proliferation only of DNCB-primed lymphocytes. The relative potential of DC populations prepared from FITC- and oxazolone-primed mice to induce antigen-specific and non-specific stimulation was dependent upon both the concentration of chemical used for sensitization and the period of exposure.