Background: Studies conducted in vitro and in animals suggest that cytokine signals to monocytes or macrophages by interferon gamma are important in the containment and clearance of disseminated nontuberculous mycobacterial infections.
Methods: We studied seven patients with refractory, disseminated nontuberculous mycobacterial infections who were not infected with the human immunodeficiency virus. Three patients were from a family predisposed to the development of Mycobacterium avium complex infections; four patients had idiopathic CD4+ T-lymphocytopenia. Their infections were culture- or biopsy-proved, involved at least two organ systems, and had been treated with the maximal tolerated medical therapy. Cellular proliferation, cytokine production, and phagocyte function were assessed in peripheral-blood cells. Interferon gamma was administered subcutaneously two or three times weekly in a dose of 25 to 50 micrograms per square meter of body-surface area in addition to antimycobacterial medications. Clinical effects were monitored by cultures, biopsies, radiographs, and in one patient a change in the need for paracentesis.
Results: In response to phytohemagglutinin, the production of interferon gamma by mononuclear cells from the patients was lower than in normal subjects (P < 0.001), whereas stimulation with ionomycin and phorbol myristate acetate led to normal production of interferon gamma in the patients. Within eight weeks of the start of interferon gamma therapy, all seven patients had marked clinical improvement, with abatement of fever, clearing of many lesions and quiescence of others, radiographic improvement, and a reduction in the need for paracentesis.
Conclusions: Interferon gamma in combination with conventional therapy may be effective for some cases of refractory disseminated nontuberculous mycobacterial infection.