Table 3.

Microscopic lesions and viral antigen distribution in chickens inoculated with clade 2.3.4.4a-e highly pathogenic avian influenza viruses, 2 days post-inoculation.

Tissue	Lesions	Cell types expressing virus antigen
Nasal cavity	Epithelial cell necrosis and desquamation, rhinitis, sinusitis, mononuclear cell infiltrates, heterophilic rhinitis	Vascular endothelial cells, vascular endothelial cells of mucosal glands, nasal epithelial cells, respiratory epithelial cells, nasal gland epithelium, mononuclear cells
Trachea	Focal necrosis, lymphoplasmacytic infiltrates	Pseudostratified epithelial cells, vascular endothelial cells, sternotrachealis muscle
Lung	Interstitial pneumonia, edema, congestion, necrosis, lymphoplasmacytic infiltrates	Vascular endothelial cells, pneumocytes, mononuclear cells
Heart	Focal necrosis of myocardiocytes	Myocardiocytes, vascular endothelial cells
Brain	Neuronal necrosis, gliosis, chromatolysis of Purkinje cell layer	Neurons, Purkinje cells, ependymal cells, glial cells, vascular endothelial cells
Intestine	Focal necrosis, lymphoplasmacytic infiltrates in submucosa	Villi enterocytes, vascular endothelial cells, mononuclear cells in lymphoid associated tissue, smooth muscle cells
Pancreas	Degeneration of individual pancreatic acinar cells, focal lymphoplasmacytic infiltrates	Acinar cells, duct cells, vascular endothelial cells
Liver	Focal necrosis, lymphoplasmacytic infiltrates	Kupffer cells, hepatocytes, vascular endothelial cells, macrophages
Spleen	Multifocal necrosis, hemorrhages, lymphoid depletion	Mononuclear cells, vascular endothelial cells
Thymus	Focal to multifocal necrosis in medullary area (evident in Hassall's corpuscles), lymphocyte depletion, apoptotic lymphocytes in cortex area	Mononuclear cells, thymic epithelium in medullary area, vascular endothelial cells
Cloacal bursa	Lymphocyte necrosis and apoptosis, lymphocyte depletion, phagocytic hyperplasia	Mononuclear cells, medullary support cells, vascular endothelial cells
Kidney	Focal necrosis of tubular epithelium with lymphoplasmacytic infiltrates	Tubular epithelial cells, glomerular cells, vascular endothelial cells
Skeletal muscle	No lesion	No lesion