Study On The Response Of Immune System In Tree Sparrow To Environmental Heavy Metals Pollution

In recent years,with the development of modern industry and agriculture,heavy metals brought into environments with atmosphere,water and soil are influencing the survival of animals and plants in varying degrees.As senior consumers in the food chain of ecosystem,birds can easily accumulate heavy metals through skin,respiratory and food chains pathways,which have a certain impact on their growth,development,breeding,respiration,reproduction,immunity and so on.The immune system is especially more sensitive to environmental heavy metals pollution.However,there is no systematic study about what are the effects of long-term heavy metals exposure to the immune system of birds and how do they respond conversely has been reported so far.In order to explore the response rules of immune system in birds,tree sparrow?Passer montanus?,a passerine widely spread over Eurasia,was chosen as the study object,and Silong town in Baiyin?BY?district polluted by heavy metals Copper?Cu?,Zinc?Zn?,Lead?Pb?,Cadmium?Cd?for long time,and the Liujiaxia?LJX?town in Yongjing district relatively unpolluted area were chosen as the study sites.The differences of body condition,immune organ,immune cell and immune molecule of nestling,juvenile and adult?male/female?in tree sparrow between BY and LJX were investigated and analyzed.The main results are shown as follows:1.Heavy metals accumulation in the main immune organ of tree sparrow from BY and LJX.The results of heavy metal levels of spleen and bursa fabricius showed that Cu,Zn,Pb,Cd concentrations of spleen in nestling,juvenile and adult?female?from BY were higher than those from LJX?P<0.05?,however,only Zn and Pb concentrations of spleen in adult?male?were higher than those from LJX?P<0.05?,and four heavy metal concentrations of bursa fabricius in nestling and juvenile were higher than those from LJX?P<0.05?.The results showed that the main immune organ of nestling and juvenile had significantly environmental heavy metals accumulation.2.Body condition of tree sparrow from LJX and BY.There was no significant difference on body weight,body length,tail length,wing length,tarsus length and beak length of nestling,juvenile and adults from LJX and BY?P>0.05?,however,body condition of nestling from BY was lower than that from LJX?P<0.01?,and it was negatively correlated with Cd concentrations.It suggested that heavy metals pollution caused a significant effect on body condition of nestling.3.Immune organ of tree sparrow from LJX and BY.Organ coefficients of spleen in nestling,juvenile,adults from BY were lower than those from LJX?P<0.01?,as well as organ coefficients of bursa fabricius in nestling,indicating heavy metals pollution caused spleen and bursa fabricius tend to smaller.Analysis spleen and bursa fabricius microstructure,the periarterial lymphatic sheath?PALS?cells density of spleen in nestling and juvenile from BY was lower than that from LJX?P<0.05?,and it was negatively correlated with Cu concentrations.Lymphoid follicular cell density of bursa fabricius in nestling and juvenile from BY was lower than that from LJX?P<0.05?,and thickness of the epithelial cell surrounding the lymphoid follicles was higher than that from LJX?P<0.05?,however,lymphoid follicular cells density and thickness of the epithelial cell was no singnificant correlation with heavy metal concentrations.The results indicated that heavy metals pollution may lead spleen and bursa fabricius tend to smaller and lymphocyte fewer in nestling,however,no significant correlation with heavy metal concentrations was found.4.Immune cell of tree sparrow from LJX and BY.There was no significant difference on the number of lymphocyte and heterophil in nestling,juvenile,adults from LJX and BY?P>0.05?.However,heterophil/lymphocyte?H/L?value of nestling and juvenile from BY was higher than that from LJX?P<0.05?,and it was positively correlated with Cd concentrations.Hematocrit?Hct?in nestling from BY was lower than that from LJX?P<0.05?,and it was negatively correlated with Cu and Cd concentrations.The results showed that heavy metals pollution caused increase of H/L value in nestling and juvenile and decrease of Hct in nestling.5.Immune molecule of tree sparrow from LJX and BY.Plasma total complement protein(CH₅₀),immunoglobulinA?IgA?,interleukin-2?IL-2?,interleukin-6?IL-6?concentrations in nestling and juvenile from BY were higher than those from LJX?P<0.05?.However,immunoglobulinY?IgY?concentrations in nestling and juvenile,and IgA and IL-6 concentrations in adult?female?were lower than those from LJX?P<0.05?.The results indicated that immune molecule of tree sparrow had significant differences under heavy metals pollution.In conclusion,by detecting Cu,Zn,Pb,Cd concentrations in main immune organ and investigating body condition,tissue structure and some function indicators of immune system in nestling,juvenile and adults,we found that the main immune organ had higher heavy metal concentrations,while body condition of nestilng from BY was lower than that from LJX,meanwhile,spleen and bursa fabricius sizes in nestling and juvenile from BY were smaller than those from LJX,as well as Hct in nestling was lower than that from LJX,H/L value and some immune molecule levels in nestling and juvenile from BY were higher than those from LJX,however,some immune molecule levels in adult?female?from BY were lower than those from LJX.In a word,compared with adults,immune system of nestling and juvenile has a more significant stress response to environmental heavy metals pollution.