Abstract: Through acute and subacute canine distemper virus (CDV) cases, we used to chose lung as the best material to isolate the canine distemper virus. But in accordance with the results observed from immunohistochemistry experiment, the lymphoid tissue of domestic dog with canine distemper virus present a strong antigen immunopositive, while there are only a few macrophage cells and epithelium of bronchi showing immunopositive. After infection of CDV, the virus proliferate in the lymph tissue, cause a long lasting and profound impairment of celluar and humoral immune function charactristed by immunosuppression, lymphocyte(B and T cells) loss,and leucopenia, rendering animals highly susceptible to opportunistic infections, which become the lethal factor in the death of animal. Although the lung has present a severs lesion, it is not the location of CDV. So the lymphoid tissue was the optimal organ to isolate CDV. 

Key words: canine distemper virus; immunohistochemistry; lymph node