The interaction of Corynebacterium equi and equine alveolar macrophages in vitro.

The in-vitro interaction of Corynebacterium equi and foal alveolar macrophages was examined qualitatively and quantitatively using cells collected by sequential bronchoalveolar lavage at 2-week intervals from birth until 14 weeks of age. Total and differential counts were performed on the recovered cells. Macrophages were identified using the non-specific esterase strain. Cultures of the alveolar macrophages were challenged with C. equi suspensions and the process and extent of ingestion was examined by light and electron microscopy. Few macrophages were recovered from the lungs of foals less than 20 days old. The numbers increased with age in a biphasic pattern. The majority of the recovered cells were alveolar macrophages. Foal alveolar macrophages were capable of significant ingestion of C. equi only in the presence of immune serum. The ingestion of C. equi by foal alveolar macrophages was confirmed by electron microscopy.