Cytotoxic activity of cells recovered from the respiratory tracts of chickens inoculated with infectious bronchitis virus.

Previously uninoculated control chickens and chickens exposed to infectious bursal disease virus (IBDV) at 1 day of age were intranasally exposed to the M41 strain of infectious bronchitis virus (IBV) at 5 wk of age. Between 7 and 13 days after inoculation with IBV, cells were collected from the respiratory tracts of both groups of chickens and assayed for in vitro cytotoxic activity against a lymphoblastoid LSCC-RP9 target cell line using a 4-hr 51chromium-release assay (CRA). Compared to thymocytes from uninfected chickens, which were used as negative controls in the CRA, respiratory tract cells from both groups consistently displayed significant cytotoxic activity against LSCC-RP9 target cells. This cytotoxic activity, attributed to natural killer cells, was statistically more pronounced (P < 0.05) in IBDV plus IBV-infected chickens than in chickens inoculated with IBV alone.