Role of interleukin-6 in determining the course of murine Tyzzer's disease.

Clostridium piliforme is an obligately intracellular bacterium that causes enterohepatic disease in many domestic and laboratory animal species. Susceptibility to infection is known to vary with the host immune status, species and strain, but little is known about specific immune mechanisms that regulate this disease. Subclinical infection was induced in weanling C. piliforme-susceptible DBA/2 or resistant C57BL/6 mice with either a toxic or a non-toxic C. piliforme isolate. Hepatic lesions and bacteria were evident in both mouse strains for 14 days after inoculation with the toxigenic bacterial isolate, but were never demonstrated following inoculation with the non-toxigenic isolate. All mice demonstrated increased interleukin-6 (IL-6) levels that were largely independent of host strain susceptibility to infection or virulence of the bacterial isolate. The severity of C. piliforme-induced hepatic lesions was increased by polyclonal anti-IL-6 treatment in both resistant (DBA/2) and susceptible (C57BL/6) mouse strains. These data indicate that IL-6 is important in mediating the course of murine C. piliforme infections but is not involved in determining host susceptibility to acute infection, nor is it influenced by the virulence of the C. piliforme isolate.