HUMAN SKIN LYMPH DERIVED FROM IRRITANT AND ALLERGIC CONTACT-DERMATITIS - INTERLEUKIN-10 IS INCREASED SELECTIVELY IN ELICITATION REACTIONS

Background: Recent reports suggested an immunomodulatory role for inte rleukin 10 (IL-10) in contact hypersensitivity. Objective: To investig ate if IL-10 is important in the regulation of irritant and allergic c ontact dermatitis (CD), IL-10 and interferon gamma (IFN-gamma) protein levels were measured in normal skin lymph, in lymph derived from irri tant and allergic (primary sensitization and elicitation) CD and in sk in blister fluid from an elicitation reaction. Methods: A superficial lymph vessel was cannulated microsurgically on the lower leg of 18 hea lthy volunteers. Lymph was collected twice daily. Protein levels of IL -10 and IFN-gamma were determined using commercially available ELISA k its and messenger RNA was estimated by a severse-transcriptase polymer ase chain reaction (PCR) method. Results: Whereas the IL-10 levels in lymph derived from irritant CD and primary sensitization of allergic C D, similarly to those obtained from normal untreated skin, remained be low 4.4 pg/ml, the n-10 levels increased manifold both in the primary allergic reaction (928.5 pg/ml) and the elicitation of allergic CD (12 4 pg/ml). The levels of IFN-gamma also increased in all volunteers exh ibiting an eczematous skin reaction and showed a tendency to be invers ely correlated with IL-10, Using a reverse-transcriptase PCR, the expr ession of n-10 and IFN-gamma in cells from lymph and from blister flui d was examined. While signals for IFN-gamma were not found, specific t ranscripts for IL-10 were detected in all samples examined, indicating that cells circulating in the lymph may also contribute to the IL-10 production measured. The IL-10 mRNA signal, however, was markedly stro nger in lymph and epidermal blister cells from the elicitation reactio ns as compared to the signal in lymph cells derived from normal skin a nd from the primary sensitization of allergic CD. Conclusion: IL-10 ma y limit and down-regulate elicitation reactions by inhibiting cytokine and antigen-presenting cell functions in the skin and in the skin-ass ociated lymphoid tissue.