Evaluation Of Chicken Immunosuppressive Model By Intramuscular Injection Of Adrenocorticotropic Hormone And The Antagonistic Effect Of Avin β-defensin-6

Stress-induced immunosuppression is a major threat to the poultry industry. Inorder to study the effect of avianβ-defensin on stress-induced immune suppression,firstly the model of chicken stress-induced immunosuppression was build byintramuscular injection of adrenocorticotropic hormone, and evaluated by means ofmorphological and immunological research methods. On the basis of this, the effect ofavin β-defensin-6on stress-induced immune suppression was evaluated.1Establish and evaluation of immunosuppressive modle by intramuscularinjection of exogenous ACTHAfter leg intramuscular injection of ACTH with the dose of0,15,30,45IU/kgBW d to21-days-old Roman Brown egg rooster (170±20g) for7d, the model wasevaluated by physiology and immunological parameters. The results are as follows.The weight, thymus index,spleen index and bursal index of the group of45IU/kgBWwas significantly lower than the control group（p＜0.05), the number oflymphocyte reduce significantly and stromal hyperplasia in immune organ.The concentration of serum corticosterone and adrenal index was elevated withthe ACTH dose-dependent; and the level of corticosterone and adrenal index of45IU/kgBW group was higher than that of the control group （p＜0.05), andhypertrophy and hyperplasia of the adrenal cortex was obviously.The level of serum IgG, IgA, IL-2and IFN-gamma of each dose group, wasdecline in ACTH dose-dependent, and was significant difference between each dosegroup（p＜0.05).The surface density of IgG positive reaction in bursa and spleen, and avianbeta-defensin positive reaction in bursa, spleen, intestine and liver in each dose group,show the decline of the ACTH dose-dependent, and the difference between the groupswas significantly（p＜0.05).The levels of blood glucose was significantly higher than that in the control grouponly two hours after the injection of ACTH（p＜0.05); then returned to normal overtime, and was no significant difference between each dose group.Our study shows, chicken stress-induced immune supression was caused byintramuscular injection in15,30,45IU/kgBW d of ACTH for7consecutive days. Theelevated level of serum corticosterone and adrenal hypertrophy and adrenocorticalcells hypertrophy can be used to evaluate the sustained stress, blood glucose is notsuitable for evaluation of continued stress. The following parameters can be used for the evaluation of immune suppression, including atrophy of immune organs, the declinedlevel of the number of immune cells and surface density of IgG and avian beta-defensin-6positivereaction in in immune organ, and the reduced level of serum IgG, IgA, and IFN-gamma and ofIL-2.2Antagonistic effect of AvBD6on stress-induced immunosuppressionThe chickens were divided into five groups, the control group which wasinjected PBS; the ACTH group which was injected ACTH with the dose of25IU/kgBW d; the BD6group which was injected AvBD6with the dose of10μg/kgBW d; the A/BD6group which was injected advancedly ACTH of25IU/kgBW d for3days, then injected AvBD6of10μg/kg BW d for6days; the the BD6/Agroup whichwas injected advancedly AvBD6of10μg/kg BW d for3days, then injected ACTH of25IU/kgBW d for6days. The samples were collected and analyzed after injection.The blood glucose and body weight was no signifent difference between each group.The thymus index, spleen index and bursal index of the BD6group wassignificantly higher than the control group（p＜0.05); the thymus index, spleen indexand bursal index of the ACTH group was significantly lower than the control group（p＜0.05), but adrenal index was higher than the control group（p＜0.05). the organindex of A/BD6and BD6/A group was no significant difference compared with thecontrol group. Plasma corticosterone concentration of ACTH group was significantlyhigher than other four group between which corticosterone levels were no differences.Circulating IgG and IgA levels of BD6group was significantly higher than that of CKgroup (p <0.05), that of CK group was significantly higher than that of ACTH group(p <0.05), and the Circulating IgG and IgA levels were no difference among theA/BD6group, BD6/A, and CK. AvBD6can significantly improve the level of IL-1,IFN-gamma (p <0.05) compared with the control group. AvBD6which was injectedfor3days in advance, can significantly antagonize the decreased level of IL-1, IL-2,IFN-γ and TNF-alpha induced by ACTH. AvBD6which was injected after3days ofACTH injection in advance, can significantly antagonize the decreased level of IL-2,IFN-γ and TNF-alpha induced by ACTH.The above tests can be concluded that, the10μg/kg BW d of AvBD6caneffectively antagonistic the immune suppression by25IU/kgBW d of ACTH.Theresults of this study has some scientific significance for understanding the immuneregulatory function of avian defensin on the stress-induced immune suppression in thepoultry.