Abstract
Summary
This experiment was conducted in an attempt to elucidate a postneonatal function for the thymus in chickens. Twenty-six chickens were thymectomized at 2 weeks of age and 26 were sham-operated. At 8 weeks of age all birds were irradiated with 750 R. Plasma protein and leukocyte values were measured in survivors. Three days after irradiation a 40-50% decrease in plasma protein occurred in control and thymectomized birds. This decrease was due to decreased amounts of albumin, and alpha-2, beta-2, and gamma globulin. By day 6 all of the globulins recovered to preirradiation levels, and in most cases there was an overcompensation noticeable by day 10. The albumin values, however, never returned to the magnitude of the starting values. No differences were observed between plasma protein responses of thymectomized and intact birds. Thymectomy caused a depression in the number of circulating small lymphocytes. The numbers of all lymphocyte types were markedly depressed by irradiation but they rebounded by day 6. Medium and small lymphocyte numbers did not recover as rapidly in thymectomized as in sham-operated birds. It is postulated that the postnatal avian thymus may contribute to the populations of small and medium lymphocytes.
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