Organ weights, T-cell proliferation, and graft vs host capabilities of hypothyroidic chickens.

Thiouracil-induced hypothyroidism reduced the thymus weights of young chickens. Thyroid weights were greater in thiouracil-fed (TF) chicks, and the circulating levels of triiodothyronine and thyroxine were lower. Thiouracil treatment resulted in higher relative adrenal weights and serum corticosterone concentrations. Absolute weights of adrenals were equivalent between control and TF groups. The TF chicks showed depressions of total white blood cell counts and numbers of lymphocytes. Monocyte and granulocyte numbers were unchanged from those of controls. Thiouracil treatment lowered the phytohemagglutinin M responsiveness of peripheral blood leukocytes (PBL). On the other hand, the PBL from TF chicks produced the higher graft vs host (GvH) response. Therefore, while the hypothyroidic state impaired cycling activity in T cells, this condition did not significantly influence a functional parameter of T cells, the GvH response.