Investigation of inducible nitric oxide synthetase, CD3 and CD8 immune-expressions in naturally infected lamb pneumonias with respiratory syncytial virus

Respiratory syncytial virus (RSV) is an RNA virus that belongs to the Pneumovirus genus of the Paramyxoviridae family. The aim of this study was evaluating the expressions of inducible nitric oxide synthetase (iNOS), CD3 (pan T cells), and CD8 (cytotoxic T cells) in lamb lungs naturally infected with RSV using the immunohistochemistry (IHC) method. For this purpose, 100 pneumonia and 10 control lung tissue samples were taken from lambs slaughtered in the slaughterhouse after macroscopic examination. The samples were fixed in 10% neutral formalin and embedded in paraffin using routine methods. Sections of 5 μm in thickness were cut. The streptavidin–peroxidase method (ABC) was used for staining the sections for IHC examination, which revealed RSV positivity in 18 tissues. These positive cases were then evaluated for iNOS, CD3, and CD8 immunostaining. In all these cases, an increase in iNOS expression was detected compared with control, whereas CD3+ T lymphocytes were detected in 14 cases and CD8+ T lymphocytes were detected in five cases. Given the increase of iNOS immunoexpression in all RSV-positive cases and increase in the number of CD3 T lymphocytes in most cases, it was concluded that iNOS and CD3+ T lymphocytes play an important role in the immune response in lamb pneumonia arising due to natural infection with RSV. Key Words: CD3, CD8, Immunohistochemistry, iNOS, Lamb, Rsv