Interaction of Rhodococcus equi with phagocytic cells from R. equi-exposed and non-exposed foals

S. K. Hietala, A. A. Ardans

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93 Scopus citations


The interaction of Rhodococcus equi with alveolar macrophages from adult horses, foals experimentally exposed to R. equi (sensitized foals) and non-exposed foals was studied using in vitro bactericidal assays, cytochemical staining and transmission electron microscopy. It was demonstrated that R. equi is a facultative intracellular parasite, able to survive and multiply within the alveolar macrophages of the host by interfering with phagosome-lysosome fusion. Opsonization of R. equi with antibody against capsular components was associated with increased phagosome-lysosome fusion and significantly enhanced (P<0.05) killing of the organism by alveolar macrophages from non-exposed foals. Macrophages from non-exposed foals were able to ingest the non-opsonized organism, but unable to kill > 65% of the infective dose by 6 h post-exposure. Alveolar macrophages from sensitized foals behaved as adult macrophages, able to kill > 95% of the infective dose by 6 h. Lymphocyte factors, derived by in vitro incubation of sensitized peripheral blood lymphocytes with R. equi surface antigens, enhanced macrophage bactericidal activity. Macrophages from non-exposed foals incubated in the presence of the lymphocyte factors had a 50% increase in killing of R. equi, while sensitized macrophages incubated with lymphocyte factors had a > 100% increase in killing capacity.

Original languageEnglish (US)
Pages (from-to)307-320
Number of pages14
JournalVeterinary Microbiology
Issue number3
StatePublished - Jan 1 1987
Externally publishedYes

ASJC Scopus subject areas

  • Microbiology
  • veterinary(all)


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