Phagocytosis of Leishmania infantum promastigotes by monocytes isolated from Leishmania-infected dogs.

Fifteen dogs with generalised leishmaniasis have been evaluated for their monocyte capacity to ingest Leishmania promastigotes. These cells displayed a lower phagocytic ability when compared to monocytes recovered from normal dogs. Moreover, sera from Leishmania-infected dogs caused a remarkable decrease of monocyte phagocytic ability in healthy dogs, whereas sera from healthy dogs could restore monocyte phagocytosis in sick animals. Similar results were seen when Candida albicans was used as stimulant. Interestingly, supernatants from polyethylenglycole (PEG) treated sera from Leishmania-infected dogs did not inhibit monocyte phagocytosis either in the autologous or in the homologous (healthy dogs) system. This suggests a possible role for serum factor(s) in the impairment of phagocytosis in Leishmania infection.