Hypothyroidism and antibody production in immature male chickens.

This study was conducted to determine if hypothyroidism has an effect on humoral immunity in immature male chickens. Two week old Single Comb White Leghorn male chicks were used as experimental animals. Two experiments were conducted using different methods to induce hypothyroidism. In Experiment 1, birds were surgically thyroidectomized (Tx group) and in Experiment 2, hypothyroidism was induced by supplementing the feed throughout the experiment with 0.1% propylthiouracil (PTU group). Antibody production against sheep red blood cells (SRBC) (thymus-dependent antigen) and Brucella abortus (BA) (thymus-independent antigen) was tested at 4 weeks of age. Serum concentrations of T4 and T3 were measured in birds from each treatment group at 5 and 9 weeks of age. Body weights were recorded and birds were then autopsied and thyroid gland weights were measured. Hypothyroidism was successfully induced in both Tx and PTU birds, as reflected by significant reduction in body weights in both groups, enlargement of thyroid glands in PTU birds and absence of thyroid glands in Tx birds. Though T4 and T3 were reduced in sera of treated birds, considerable amounts of these hormones were detected. Hypothyroidism did not seem to have profound or consistent effects on antibody production against SRBC or BA. The possibility that thyroid hormones play a role in antibody production was not ruled out. However, it was suggested that within the physiological range of thyroid gland activity, thyroid hormones may not significantly regulate antibody production.