Human peripheral lymphocytes, identified as T o r B cells with a fluorescent anti-globulin serum, were studied in two varieties of rosette formation:(1) with sheep red corpuscles, a phenomenon shown by a large proportion of human lymphocytes and totally different from that observed in the mouse; and (2) with human red cells sensitized with incomplete anti-Rh. Lymphocytes forming sheep cell rosettes were never fluorescent; i.e. they were T cells. 73 % of lymphocytes forming sensitized-cell rosettes were fluorescent B cells. Horse anti-human lymphocyte serum inhibits the first but not the second variety of rosette formation.

Cell-mediated immunity has been studied in patients with 1) megaloblastic anemia of folic acid deficiency, 2)megaloblastic anemia of pregnancy, or 3) iron-deficiency anemia. Using dinitrochlorobenzene skin tests, phytohemagglutinin-stimulated lymphocyte transformation, and rosette inhibition by antilymphocyte globulin, we have shown that cell-mediated immunity is depressed in megaloblastic anemia due to folate deficiency; this depression was reversed by folate treatment. Cell-mediated immunity was not impaired by iron-deficiency anemia. Suggested interactions between iron deficiency and folate metabolism were not clarified by these studies.

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