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

Vet Microbiol. 1987 Aug;14(3):307-20. doi: 10.1016/0378-1135(87)90118-0.


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 less than 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 greater than 65% of the infective dose by 6 h post-exposure. Alveolar macrophages from sensitized foals behaved as adult macrophages, able to kill greater than 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 greater than 100% increase in killing capacity.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Actinomycetales Infections / physiopathology
  • Actinomycetales Infections / veterinary*
  • Animals
  • Animals, Newborn
  • Female
  • Horse Diseases / microbiology*
  • Horse Diseases / physiopathology
  • Horses / physiology*
  • In Vitro Techniques
  • Macrophages / physiology*
  • Macrophages / ultrastructure
  • Opsonin Proteins / immunology
  • Pulmonary Alveoli / cytology*
  • Rhodococcus / physiology*
  • Rhodococcus / ultrastructure


  • Opsonin Proteins