Subcutaneous interferon-beta injections in patients with multiple sclerosis initiate inflammatory skin reactions by local chemokine induction.

Subcutaneous Interferon-beta (IFN-beta) injections for the treatment of multiple sclerosis (MS) frequently cause inflammatory injection site reactions. To study the role of chemokines we obtained skin biopsies from 7 MS patients 24 h after injection. At the IFN-beta but not at the contralateral placebo injection sites, we observed strong IP-10/CXCL10 and moderate MCP-1/CCL2 expression associated with extensive perivascular, highly CXCR3-positive T cell and macrophage infiltrates. Primary human skin cells displayed a comparable pattern of chemokine induction after stimulation with IFN-beta in vitro. IFN-beta may therefore trigger inflammatory skin reactions through local chemokine induction followed by rapid immune cell extravasation.