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Ability to form autologous rosettes (A-rosettes) is characteristic of a certain population of immature T cells, present in the thymus of various species including man. In mice, few A-rosettes are normally found in peripheral blood and spleen but their number increases markedly in spleen following thymectomy. In our studies, A-rosette formation could be demonstrated to be significantly enhanced in the spleen of C57B1/Ks mice after the animals had been maintained 3, 6, and 8 weeks on a zinc-deficient diet (Zn − ) and to increase progressively with duration of feeding the Zn − diet. These changes were quickly reversed by feeding a normal diet containing zinc but could not be eliminated by complete adrenalectomy, a finding that ruled out their dependence on pituitary-adrenal as is function attributable to stress. Pair-fed controls and mice fed a zinc-supplemented diet ad libitum showed few A-rosettes, as expected.

The effect of zinc deficiency (Zn − ) on the circulating thymic hormone (FTS) levels in A/J mice was studied. After 3 weeks of feeding the mice a Zn − diet, FTS levels were markedly reduced and after 17 weeks, FTS was undetectable. By contrast, the zinc-supplemented (Zn + ) group seemed to maintain FTS levels better than the normal diet group with aging. On the other hand, spleen spontaneous rosette-forming cells (sRFC) were studied for their azathioprine (AZ) sensitivity in A/J mice on different diets. The Zn − mice had fewer sRFC than did the normally fed or Zn + mice. The role of zinc in controlling levels of FTS and thus thymic function is discussed.