Distinct ability to accumulate eosinophils during the inflammatory cellular response to M. Bovis BCG in the mouse pleural cavity

Abstract.

Objective and Design: The host response to Mycobacteria focuses on the development of cell-mediated immunity and granuloma formation. Here, we investigated the onset of cellular responses to mycobacteria in murine pleurisy.¶Material: Distinct mouse strains previously described as Bcg susceptible or resistant were inoculated intrathoracically with different doses of live M. bovis BCG.¶Methods: At various time intervals, cells harvested from the inflammatory site were identified and ultra-structurally analysed.¶Results: BCG-induced pleurisy had two peaks of cellular influx at 1 and 15 days after infection. At the first half hour, macrophages were found to be heavily infected. Neutrophil arrival started after 2 h of infection and peaked at 4 h. At this time, neutrophils were found ingesting mycobacteria exclusively with a high infecting dose. BCG was potently more eosinophilotactic in Bcg susceptible mice than in the resistant ones and to other well known eosinophilia inducers: IL-5, PAF-acether or LPS.¶Conclusions: Mycobacterial load and mouse susceptibility seem to determine the early granulocyte dynamics in the lesion.