Study of CD11c and CD169+ genes expression using immunohistochemistry technique in broilers infected with CRD

Avian Chronic Respiratory Disease (CRD) syndrome is a respiratory infection in chickens caused by many etiological agents, including Mycoplasma spp. Escherichia coli and some viruses, leading to pneumonia, air sacculitis, and septicemia, which are associated with high morbidity and mortality. This study aimed to evaluate immunological aspects, including marker expression for dendritic cells (CD11c) and respiratory macrophages (CD169+), in CRD broiler farms using immunohistochemistry, and to assess some pathological changes in these broilers. Fifty tracheal and lung histopathological section samples were from CRD-infected broilers used to detect pathological changes and to evaluate marker expression of dendritic cells (CD11c) and respiratory macrophages (CD169+). The results revealed severe tracheitis with vascular congestion, extensive epithelial cell necrosis, and inflammatory cell infiltration. The lung showed severe serofibrinous pneumonia with increased fibrous tissue, inflammatory cell infiltration, hyperemia, and blood vessel congestion, as demonstrated by hematoxylin and eosin staining. An immunohistochemistry study revealed intense expression of CD169+ macrophage cells and moderate expression of CD11c DCs in the lung sections of infected birds with CRD and moderate expression of CD169 macrophages and CD11c DCs in trachea sections of infected birds with CRD in comparison to lung sections of normal birds that revealed very weak to negative expression for each of them, respectively. It concluded that immunohistochemistry can be used to detect marker expression in dendritic cells (CD11c) and respiratory macrophages (CD169+), which determine the immunological state in birds infected with CRD.