Effects of propylthiouracil (PTU) on the immunological status of the chicken

Effects of propylthiouracil (PTU) using different treatment schedules on immune functions in young male chicken were studied. Antibody productions to sheep red blood cells (SRBC) and Brucella abortus (BA) were found to rise in the chicks treated with 0.1% and 1% PTU. Furthermore, the chicks treated with 1% PTU exhibited a significantly greater reaction to phytohemagglutinin (PHA) in skin test using the wing web than the control did. Treatment of 5% PTU, however, inhibited the antibody productions to SRBC and BA and the reaction for the skin test to PHA. Antibody titers to both antigens and serum IgG level were lower in the chicks after cessation of PTU treatment. The most conspicuous histology was the lymphatic depletion of the lymphoid organs in chicks treated with 5% PTU. The bursa of Fabricius, thymus and spleen were severely atrophied. The total WBC and the number of lymphocytes and monocytes were significantly reduced in the presence of 0.1% and 1% PTU at 8 weeks of age. Although, concentrations of serum thyroxin (T4) and 3,5,3'-triiodothyronine (T3) were significantly lower in the chicks treated with all doses of PTU, the cessation of the treatment was followed by an increase in the concentrations of serum T4 and T3 to levels not different from in the untreated control chicks. These data showed that PTU at 0.1% and 1% concentrations did not suppress immune responses in chickens unlike the case reported in mammals.