Use of recombinant interferon gamma administered intramuscularly for the treatment of psoriasis.

Twenty-three patients with chronic plaque-type psoriasis were treated with intramuscular administration of human recombinant interferon gamma. Patients were treated with doses of 0.01 to 0.25 mg/m2 daily (five out of seven days) for four weeks, or 0.25 mg/m2 three times weekly for one week with escalation to 0.5 mg/m2 for the subsequent seven weeks. Some patients treated with the 0.25-mg/m2 dose showed improvement coincident with their therapy. Although recombinant interferon gamma may have some therapeutic activity in certain patients' psoriasis, the magnitude of this effect is at best small. This result is in contrast to interferon alfa, which has been reported to cause an exacerbation of this disease. Staining of posttreatment biopsy specimens with a monoclonal antibody against HLA-DR antigen using an immunoperoxidase technique demonstrated HLA-DR expression by keratinocytes in some of the patients treated at the higher doses. No obvious correlation was seen between clinical improvement of the psoriasis and intensity or extent of HLA-DR antigen expression by keratinocytes in the skin biopsy specimens.