An Experimental Study on Apoptosis in Lymphoid Tissues of SPF Chicken after Avian Influenza Serotypes H9N2 Infection

Background and purpose: Influenza virus induces cell death in animals and human through necrosis and apoptosis. The present study is an attempt to experimentally examine the type of cell death in lymphoid tissue of chicken infected with avian influenza serotype H9N2 (A/chicken/Iran/772/2000). Methodology: Twenty SPF three weeks old chickens were grouped in two identical groups. The treatment group was infected by influenza virus (0.2ml, dilution 1:10, titration EID 50 107.5) and the control group received saline serum of the same volume through intranasal inoculation. Spleen, thymus, bursa of fabricius tissue specimens were collected after 72hrs. Afterward, microscopic intersections (5-6μm) stabilized in buffer formalin (10%) and marked by hematoxylin-eosin were prepared from the specimens. Findings: Histopathological examination of lymphoid tissues of the treatment and control chickens showed necrosis, apoptosis, and lymphoid depletion in lymphoid tissues of the treatment group. The difference between treatment and control groups in terms of apoptosis in spleen tissue was significant (p 0.001); however, the difference in thymus and bursa of Fabricius tissues was not significant. As to necrosis and lymphoid depletion, there was a significant difference between the two groups with regard to spleen, thymus, and bursa Fabricius tissues. (p 0.001). Conclusion: The survey showed that avian influenza serotype H9N2 can cause damages to lymphoid tissues through inducing apoptosis and necrosis.