LOCAL EXPRESSION OF CYTOKINES IN IDIOPATHIC INFLAMMATORY MYOPATHIES

The idiopathic inflammatory myopathies (IIM), including dermatomyositi s (DM), polymyositis (PM), and inclusion body myositis (IBM), are rega rded as autoimmune diseases. They are characterized by chronic lymphoc ytic and macrophagic infiltration in muscle tissue. Of particular impo rtance in understanding the immune response to IIM is the specific pat tern of locally produced cytokines. Frozen muscle tissues from IIM (5 DM, 3 PM, and 1 IBM) were used to investigate the cytokine responses. The RT-PCR technique was instrumental to determine the pattern of expr ession of pro-inflammatory (IL-1 beta, IL-6, TNF-alpha), Th1 (IFN-gamm a IL-2), and Th2 (IL-4) cytokines. Immunohistochemistry was also used to localize morphologically IFN-gamma and IL-4. Our results show that pro-inflammatory cytokines and Th1 cytokines are mainly expressed in I IM. The accumulation of mononuclear inflammatory cells and the inflamm atory syndrome in IIM are probably related in part to the production o f pro-inflammatory cytokines. Moreover, the pattern of local cytokine expression is consistent with a Th1 immune response related to autoimm une diseases.