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. Susce ptibility to infection is known to vary with the host immune status, specie s and strain, but Little is known about specific immune mechanisms that reg ulate this disease. Subclinical infection was induced in weanling C, pilifo rme-susceptible DBA/2 or resistant C57BL/6 mice with either a toxic or a no n-toxic C, piliforme isolate. Hepatic lesions and bacteria were evident in both mouse strains for 14 days after inoculation with the toxigenic bacteri al isolate, but were never demonstrated following inoculation with the non- toxigenic isolate, All mice demonstrated increased interleukin-6 (IL-6) lev els that were largely independent of host strain susceptibility to infectio n or virulence of the bacterial isolate. The severity of C, piliforme-induc ed hepatic lesions was increased by polyclonal anti-IL-6 treatment in both resistant (DBA/2) and susceptible (C57BL/6) mouse strains. These data indic ate that IL-6 is important in mediating the course of murine C, piliforme i nfections but is not involved in determining host susceptibility to acute i nfection, nor is it influenced by the virulence of the C, piliforme isolate .