The TNF-α and IL-1β pathways were activated in subgroups of PM and RA subjects, respectively, with another subgroup of RA subjects showing activation of the IL-13 pathway.
Muscle biopsy tissues from 10 patients with polymyositis or dermatomyositis and 7 healthy control subjects were investigated by immunohistochemistry using antibodies against IL-1 receptor type I (IL-1RI), IL-1RII, IL-1alpha, IL-1beta, and IL-1 receptor antagonist (IL-1Ra).