Role of cell-mediated immunity (CMI) in chickens inoculated with avian leukosis/sarcoma virus

Immunosuppression of chickens infected in ovo with avian leukosis virus (RAV-1) by the injection of antilymphocyte serum (ALS) did not significantly (P > 0.05) alter the incidence or distribution of lesions in chickens between 3 and 6 months of age as compared to control groups. Antilymphocyte serum treatment of Rous sarcoma virus [RSV (RAV-2)]-infected chickens significantly (P < 0.05) inhibited tumour regression and enhanced tumour metastasis. It was concluded that cell-mediated immunity was not a significant factor in effecting the survival of viraemic chickens Viraemic leukosis virus infected-chickens responded as well as normal chickens to sensitization to Mycobacterium tuberculosis H37Ra. The results were based on in vivo wattle tests and in vitro cell-mediated cytotoxicity assays. It was concluded that subclinical avian leukosis virus infection had no effect on the thymus-dependent lymphocyte (T-cell) population associated with cutaneous delayed hypersensitivity and cell-mediated cytotoxicity.