IDENTIFICATION OF DENDRITIC CELLS AS A MAJOR SOURCE OF INTERLEUKIN-6 IN DRAINING LYMPH-NODES FOLLOWING SKIN SENSITIZATION OF MICE

Skin sensitization with chemical allergens is associated with the acti vation and proliferation of T lymphocytes within lymph nodes draining the site of exposure. These events are accompanied by the secretion of interleukin-6 (IL-6) by lymph node cells (LNC). We have investigated the cellular source of IL-6 seventy-two hours following primary exposu re of mice to the contact allergen oxazolone. Immunoeytochemical analy ses of sections of activated lymph nodes have revealed that cells expr essing IL-6 are located within the T-dependent lymph node paracortex, with none present in lymphoid follicles. Cells which expressed IL-6 co fractionated exclusively with LNC of low buoyant density, the majority of which also expressed membrane Ia and had a dendritic morphology. D epletion of dendritic cells from LNC culture was associated with a sig nificant decrease in the secretion of IL-6 by the residual population. These data demonstrate that dendritic cells are a major source of IL- 6 within lymph nodes during primary immune responses to cutaneous anti gens.