The aim of (he present study was to investigate the possible effects of total bilateral thymectomy on some hematological parameters, immune responses and on the level of serum free amino acid pattern as well as serum protein and its components in the blood of Japanese quail vaccinated with Newcastle disease virus vaccine .A total number of 180 Japanese quails (Coturnix coturnixjaponica) were used in this study. The experimental work was designed into luo experiments. Experiment I: comprised 100 birds of both sexes (50 male and 50 female). At 10th. day old, birds were equally divided into 4 groups (2 groups of male and 2 groups of female), and the total bilatcral) surgical thymectomy was performed for one group of male and one group of female birds. Two weeks posl-thymectomy period blood samples were taken every week from control and thymectomized group for 5 successive week for determination of hematological parameters. Experiment II: included 80 male and female birds. A total bitatcral thymectomy was performed for 40 birds at 10 days of age and the 40 kept as intact control. Two weeks post-thymeclomy period the intact and thymectomized birds were divided into four equal groups. Groupl; intact control (non-vaccinated). GroupII: thymectomized birds (non-vaccinated). Group III: intact birds (vaccinated). Group IV: lhymectomized birds (vaccinated). Two weeks later post-vaccination blood samples were collected from nil animal groups. Serum was separated and used for determination of serum protein and its fractious, free amino acid and hacmagglutination inhibition antibody liter. Also, heparinized blood was taken for lymphocyte blastogenesis micro-assay. Two weeks post-vaccination all groups were challenged with a velogenic visccrotropic NDV strain via i.m route. The obtained results revealed that, thymectomy caused significant decrease in erythrocytic count in both male and female group, whereas PCV was significantly decreased in female group. Total leukocytic count was markedly reduced in both male and female groups. Lymphocyte percentage was significantly decreased, whereas heterophils percentage was increased in both male and female after thymectomy. Immunological study revealed that thymectomy caused marked reduction in the level of blastogenic capacity of peripheral blood lyinphocytcs induced by phytohaemagglutinin and by NDV antigen in both vaccinated and non-vaccinated thymectomized group compared with control one. Antibodies were markedly reduced after thymectomy in vaccinated groups determined by hemagglutination inhibition antibody titer. Challenge with VVNDV two weeks post-vaccination resulted in 75% protection rate in vaccinated intact control group and thymectomized one compared with a protection rate 50% in intact and 25% in thymectomized non-vaccinated group. The biochemical changes after thymectomy showed a significant decrease in the value of serum glutamic, prolinc, methiouinc and arginine concentrations, whereas serum cysteine, isoleucine and tyrosine levels revealed a significant increase in thymeclomized quail compared with intact control (groupl). There was a significant decrease in (he concentrations of serum glutamic and proline values in intact birds vaccinated with lasota strain of Newcastle disease virus (NDV) compared with intact non-vaccinated (groupl). A significant decrease in serum glycine, valine, isoleucine, tyrosine and lysine levels in thymectomized vaccinated quail with NDV. Meanwhile, serum aspartic, proline and arginine concentrations showed a significant increase when compared with thymectomized non-vaccinated (groupll). The values of scrum total protein, albumin and gamma globulin levels showed a significant decrease, whereas serum alpha-globulin level showed a significant increase in thymectomized quails compared with intact control (groupl). Serum alpha-globulin level exhibited a significant increase in intact quails vaccinated with NDV, However, serum protein and its fractions showed no significant changes in thymectomized vaccinated quails compared to thymectomized non-vaccinated (group11). The results of this study indicate that, thymus gland seems to be important for crythropoiesis. leukopoiesis, and lymphocyte number and its activity in cell mediated immune response as well as antibody formation. Also, from biochemical investigations thymus gland seems to be participates in regulation of protein and amino acids metabolism.
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