Apoptosis Of Immune Organs In Specific Pathogen Free Chicks And Commercial Broilers After Artificial Infection With CSISV

Recent years, chicken stunt and immunosupression syndrome (temporary name, CSIS) has been becoming one of important infectious diseases which break out on poultry. The disease's main syndromes are growth stunt and immunosupression. The preceding research found apoptosis happened on immune organs after CSISV infection for broiler. The apoptosis index (AI) of immune organs specific pathogen free (SPF) chicks and broilers infected with CSISV is detected by using paraffin section TUNEL assay in this experiment. It is in order to research the immunosuppressive mechanism of CSISV.It is carried out the research of broiler bursa of 72h after CSISV infection to optimize the experimental conditions of paraffin section TUNEL assay and establish the TUNEL assay to detect cell apoptosis. AI is expressed by the number of apoptotic cells per 1000 cells. The test data is expressed by mean±SD and the differences between control group and test group are analyzed by T test with SPSS13.0 software. Using the established TUNUL assay detect cell apoptosis of immune organs from 7-days-old SPF chicks and commercial broilers infected with CSISV-ZZ2004 strain. The results show:The apoptosis appear in many immune cells of bursa,thymus and spleen from SPF chicks and commercial broilers after CSISV infection.The serious extent of apoptosis in the immune organs (including bursa, thymus and spleen) of SPF chicks infected with CSISV decrease respectively. The AI of bursa is 15.532～39.386 and very significant (P<0.01) higher than control group from 6h to 1056h after infection; The AI of thymus is 6.262 and significantly (P<0.05) higher than control group on 12h after infection. The AI of thymus is 7.719～23.956 and very significant (P<0.01) higher than control group from 24h to 1056h; The AI of spleen is 3.841 and significantly (P<0.05) higher than control group on 36h after infection. The AI of spleen is 4.418～12.873 and very significant (P<0.01) higher than control group from 48h to 1056h . The curves of AI of immune organs from commercial broilers infected with CSISV are almost similar with SPF chicks. However, there are a few differences on some aspects. The peak time of apoptosis is 48～72h later than SPF chicks. For SPF chicks and commercial broilers, the medulla has significant (P<0.05) more apoptotic cells than cortex in bursa from 6h to1056h; The cortex has significant (P<0.05) more apoptotic cells than medulla in thymus from 48h to1056h; The red pulp and white pulp all have apoptotic cells in spleen and the differences are not significant (P>0.05). These mean that apoptosis of lots of pre-T cells and pre-B cells in bursa and thymus appear after CSISV infection and the lymphocytes which can differentiate to mature lymphocytes are decreased. These make the immune function descend.This explain the immunosuppression of CSISV on immune cell aspect.