ABSTRACT
Influenza virus causes the cell death in animals and human beings. Cell death occurs in two manners as necrosis and apoptosis. In this study, the types of cell death in lymphoid tissues assessed in experimentally infected chickens with H9N2 avian influenza virus [A/chicken/Iran/772/2000]. In this experimental study, 20 SPF chickens aged 3 weeks were divided equally into two groups. The treatment group was infected with 0.2 ml of 1:10 dilution and 10[7.5] EID50 titer of the virus intra-nasally and the control group was treated with saline normal in the same volume. Lymphoid organs including spleen, thymus and bursa of fabricius were collected after 72 hours of treatment and tissue specimens were fixed in 10% buffered formalin. Microscopic sections with the thickness of 5-6 micron were stained by H and E method. Histopathological examination of lymphoid tissues of the experimental groups indicated necrosis, apoptosis and lymphoid depletionsin the treatment group. Apoptotic changes in the splenic tissues were significantly different between two groups [p<0.001]. There were no significant differences between two groups in terms of changes in the thymus and bursa of fabricius. However, Necrotic changes and lymphoid depletions in the splenic tissues, thymus and bursa of fabricius were significantly different between two groups [p<0.001]. This study indicates that H9N2 avian influenza virus is able to cause lymphoid tissue damages through induction of apoptosis and necrosis