Immunologic Changes And Mechanism In Immune Organs Of Chickens Infected With Avian Influenza Virus

In this study, immunohistochemistry staining and cyto-histochemistry staining were used todiscover the changes of the contents both IgS antibody-producing cells and the quantity of CD₄⁺Tand CD₈⁺T lymphocyte subpopulation, T_ANAE⁺ cells in immune organs (thymus, bursa and spleen)of chickens infected with AIV at 7 days old and 21 days old, which were to reveal the mechanismand regularity of immunity of immune organs of chickens infected with AIV. The experimentprovided scientific evidence of experiment for the mechanism of morbidity and useful effectiveprevention in AI. The results were as follows:1. Compared with controls, the quantity of T_ANAE⁺ cells in immune issue were decreased at3～14 days post infection (P1) regardless of the chickens infected with AIV at 7 days old and 21days old at different degree; In the end of infective stage, the quantity of T_ANAE⁺ cells of twoimmune organs recovered. The observations showed that cellular immunity of chickens infectedwith AIV was critically inhibited, which was the primary element in immune subordinatechickens.2. The quantity of CD₄⁺T and CD₈⁺T lymphocyte subpopulation in thymus of chickensinfected with AIV was decreased at 3～5 days PI at different degree; the quantity of CD₄⁺T cells inspleen of infected chickens old decreased remarkably at 5～7 days and 3 days PI (p＜0.01)respectively; that of CD₈⁺T cells in spleen decreased at different degree at 3～14 days PI. In the endof infective stage, the quantities of lymphocytes of two immune organs recovered. As a result ofthe quantity of CD₄⁺T cells' rapid reduction, possibly caused the CD₈⁺T cells' function ofeliminating flu virus reduced. It indicated organism cellular immune functional disturbance, whichwas the important performance of chickens infected with AIV to present the immunosuppression.3. Compared with controls, the quantity of IgG, IgM, IgA antibody-producing cells in bursa,spleen and thymus of infected chickens decreased at 3～4 days PI(p＜0.05 or p＜0.01) at differentdegree. And the quantity of IgS antibody-producing cells began to ascend, approach to controls at21 days PI. In initial period of infection, the quantity of antibody-producing cells was decreasedrapidly and the physiological function in organism was exhausted, which were the importantreasons in lowing of immune function of infected chickens. But in the recovery stage, thesecretion of IgS is in high level. Thus the ability of resisting virus was raised.4. The research discovered that the clinical death rate of chickens infected at 21 days old washigh compared with chickens infected at 7 days old. And the humoral immune response wasslower, the antibody level was lower than the controls. The above results indicated: The immuneregulations in immune organs of chickens infected at 7 days old were more sensitive to AIV than that of infected chickens at 21 days old, which were full grown in immune system and could resistvirus effectively.The research revealed the immunity pathogenesis mechanism of AIV from the quantitychanges in avian center immune organ and peripheral immune organ antibody-producing cells andthe T cells for the first time. It provided the scientific basis to prevent AI, which had significantmeanings in theory and in practice.