The broiler chicken as a model for immunotoxicity assessment. 1. Standardization of in vitro immunological assays

The broiler chicken was developed as an alternative animal model to laboratory rodents for immunotoxicologic assessment. In vivo treatment with 100-200 mg/kg cyclophosphamide (CY) was used as a known immunosuppressive treatment to standardize the assay systems. Protocols for assessing specific immunological functions were developed in specific pathogen-free (SPF) broilers to measure lymphocyte blastogenesis to T-cell (concanavalin A and phytohemagglutinin) and B-cell (Staphylococcus aureus cells) mitogens, delayed-type hypersensitivity (DTH) to tuberculin, natural killer (NK) cell cytotoxicity, plaque-forming cell (PFC) response to sheep red blood cells (SRBC), and serum antibody titers to SRBC. CY was an effective immunosuppressant in the broiler system for assessment of lymphocyte responsiveness to mitogenic stimulation, DTH reactivity, and the antibody response to SRBC as assessed by PFC and serum antibody titers. NK cytotoxicity was not altered on a cellular level following treatment with CY at a dose that produced greater than 75% depletion of spleen cellularity. However, under these conditions, it must be assumed that the capacity of CY-treated birds to mediate NK effector functions would be reduced. These results demonstrate the applicability of the broiler chicken as an animal model for immunotoxicity testing.