The plasma histamine level was within normal range. The level of IL-6 in sera peaked to 74 pg/mL, concomitant with the peak of eosinophilia at the acute phase phase of the attack. Under corticosteroids, we observed a drop in the IL-6 serum level to 29 pg/mL, concomitant with the clinical remission. During the attack, an increase in IL-6 production was observed in 24 h blood monocyte supernatants (11.10(3) pg/mL compared with 2.4+/-0.8.10(3) pg/mL for BM from controls) as well as in skin endothelial cells but not in the blood and skin eosinophils. In vitro, when endothelial cells were incubated in eosinophils supernatants of the patient, liberation of IL-6 was observed (3.3 10(3) pg/mL compared with controls: 2.1 10(3) pg/mL) CONCLUSION: Serum IL-6 elevation may be related to an increased production by blood monocytes and endothelial cells, possibly stimulated by eosinophil mediator during the acute phase of the disease, and might participate in the inflammatory reaction of this syndrome.

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