Chemotactic response of lymphocytes in chicken embryos infected with Mycoplasma gallisepticum.

A prominent feature of Mycoplasma gallisepticum (MG) infection is a lymphoproliferative response at the site of infection. In this study, artificial air cells (AACs) were made in eggs containing 16-day old chicken embryos. An MG culture and supernates from MG-infected RP-9 cells, HD-11 cells and monocytes were separately deposited on the membranes of the AAC. After incubation for 5 days, the eggs were opened and the AAC membranes were collected for histopathological examinations. Immunolabelling of MG-infected membranes showed a massive infiltration of lymphocytes possessing CD3 surface markers and the presence of cells that secreted lymphotactin, a chemokine. The supernates from MG-infected cells caused the infiltration of comparatively small numbers of lymphocytes. The culture medium-inoculated AACs had no obvious abnormalities of the membranes. It is suggested, therefore, that MG infection of the embryonic membranes causes the embryos to secrete lymphotactin, which induces the migration and accumulation of lymphocytes to the sites of infection.