Although dietary arginine is a factor in immune function and disease resistance, the full range of effects has yet to be described. In this study, the effects of dietary arginine on leukocyte population changes were examined in the peripheral blood and the respiratory tract of chickens inoculated with infectious bronchitis virus (IBV) strain M41. At 2 wk of age, female line P2a White Leghorn-type chickens were randomly assigned to one of three diets with different arginine levels: a marginally deficient diet (0.5%), an adequate diet (1.0%), and a diet containing a high level of arginine (3.0%). All birds were inoculated with IBV at 4 wk of age, and then the peripheral blood and the respiratory lavage were collected at 1 and 7 d postinfection (DPI). The growth rate of birds that received 0.5% arginine was significantly lower than that of birds receiving 1.0 or 3.0% arginine, whereas the growth of the latter groups did not differ. The percentage and absolute number of heterophil (H) and the H/lymphocyte (L) ratio in the peripheral blood at 1 DPI significantly increased as dietary arginine increased. In the respiratory lavage at 1 DPI, the percentage of H also increased with dietary arginine increase. At 7 DPI, the percentage of CD8+ cells from birds fed the deficient diet was lower than those from birds fed the adequate diet and the diet containing a high level of arginine, whereas the cell surface density of CD8 antigen did not vary among groups. These results show that dietary arginine influences the character of the chicken cellular response to IBV and the distribution of responding leukocyte subpopulations in a target tissue for the infection.
Ochratoxin A (OA) was administered to 13-day-old chicken embryos via the chorioallantoic membrane. The 7-day LD50 value (day 20 incubation) of OA was calculated at 7.9 micrograms of OA. Ochratoxin-treated embryos (2.5 micrograms) had slight but significant changes in numbers of immunoglobulin-bearing cells in the bursa but not in the spleen. Chicks hatched from in ovo-treated eggs were challenged with 9 X 10(4) colony-forming units (CFU) of beta-hemolytic Escherichia coli (O1:K1) at 7 days of age via the thoracic air sac. Lesion scores of OA-treated chicks were equal to or less severe than those of controls. Hatchmates of the above chicks were vaccinated with a homologous killed E. coli bacterin (O1:K1) at both 2 and 4 weeks of age and challenged with 10(4) CFU of E. coli at 7 weeks. Post-challenge lesions were present in three vaccinated untreated controls and no OA-treated chicks. We conclude that although in ovo exposure to OA may marginally suppress immunoglobulin-bearing cells of bursa, chicks hatched from OA-treated eggs respond as well as controls to an antigen and resist infection by a virulent organism.
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