A role for interleukin-1 in the pathogenesis of Lyme disease.

Interleukin-1 (IL-1) is the major immunoregulatory molecule produced by macrophages in response to a variety of environmental insults including chemicals, phagocytosis, bacteria, and bacterial products. Macrophages stimulated by Borrelia burgdorferi produced large quantities of IL-1 when spirochetes were added to macrophages at a ratio of 10 spirochetes per macrophage. The release of IL-1 was dose dependent: a single spirochete per macrophage was sufficient to produce significant quantities of IL-1. Spirochetal lipopolysaccharide was not required for this activity in that polymyxin B in the spirochete-macrophage culture had no effect on IL-1 production. Normal murine fibroblasts cultured with this IL-1 were shown to have an increased rate of DNA synthesis and an increase in secreted collagenase. IL-1 was found in joint fluids from Lyme disease patients. When IL-1 was injected intradermally into the backs of rabbits, the injection sites became indurated, erythematous, and warm to the touch after 4 hrs and annular lesions much like those of erythema chronicum migrans were seen in some animals after 24 hrs. B. burgdorferi is a powerful inducer for IL-1 in vitro, and it is reasonable to presume that it acts similarly in Lyme disease patients. Our results suggest that IL-1 in turn, may play a role in many of the clinical manifestations of Lyme disease.