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 interleukin 10 (IL-10) in contact hypersensitivity.

OBJECTIVE: To investigate if IL-10 is important in the regulation of irritant and allergic contact dermatitis (CD), IL-10 and interferon gamma (IFN-gamma) protein levels were measured in normal skin lymph, in lymph derived from irritant and allergic (primary sensitization and elicitation) CD and in skin blister fluid from an elicitation reaction.

METHODS: A superficial lymph vessel was cannulated microsurgically on the lower leg of 18 healthy volunteers. Lymph was collected twice daily. Protein levels of IL-10 and IFN-gamma were determined using commercially available ELISA kits and messenger RNA was estimated by a reverse-transcriptase polymerase chain reaction (PCR) method.

RESULTS: Whereas the IL-10 levels in lymph derived from irritant CD and primary sensitization of allergic CD, similarly to those obtained from normal untreated skin, remained below 4.4 pg/ml, the IL-10 levels increased manifold both in the primary allergic reaction (928.5 pg/ml) and the elicitation of allergic CD (124 pg/ml). The levels of IFN-gamma also increased in all volunteers exhibiting an eczematous skin reaction and showed a tendency to be inversely correlated with IL-10. Using a reverse-transcriptase PCR, the expression of IL-10 and IFN-gamma in cells from lymph and from blister fluid was examined. While signals for IFN-gamma were not found, specific transcripts 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 stronger in lymph and epidermal blister cells from the elicitation reactions as compared to the signal in lymph cells derived from normal skin and from the primary sensitization of allergic CD.

CONCLUSION: IL-10 may limit and down-regulate elicitation reactions by inhibiting cytokine and antigen-presenting cell functions in the skin and in the skin-associated lymphoid tissue.