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Levels of Facteur Thymique Serique (FTS) were measured by rosette inhibition assay in the sera of patients with mycosis fungoides (MF) and Sezary syndrome (SS). Increased levels of FTS were detected in 15 of 23 patients with MF. Two patients with SS showed normal values. The biological activity quantitated in the serum was shown by specific immunoabsorption using anti-FTS antibodies to be due to FTS and not to allogeneic factors (AF).

The effect of thymus extract on the development of cell surface antigenicity in two patients with primary immunodeficiency was studied and compared. A stem cell fraction from bone marrow preparations of a patient with severe combined immunodeficiency failed to develop cells with antigenic markers of T-lymphocytes while that of a patient with common variable form of immunodeficiency who had both severe functional deficits of T-lymphocytes and agammaglobulinemia developed cells with such markers after treatment with thymus extract. These findings indicate that the two forms of severe combined immunodeficiency disease studied have different bases which may be reflected in differences of response to differentiative influence of thymus extract.

Recently it has been found that children with severe combined immunodeficiency (SCID), who are thought to lack lymphoid stem cells capable of developing into either the B- or T-lymphocyte populations, do not possess cells in their marrow which can be induced by partially purified thymic extracts to differentiate into T-lymphocytes in vitro . The initial observations were made with marrow cells from three untreated infants with SCID under the same conditions which revealed clear evidence of induced differentiation in normal individuals. Marrow cells and peripheral blood lymphocytes from two of these children were studied again after bone marrow transplantation (BMT). Clear indication of precursor cells was obtained in marrow and blood after successful transplantation. The newly acquired precursors could be differentiated in vitro into T-lymphocytes under the influence of thymic extracts. T-cell characteristics were established both with a specific anti-human T-cell serum (ATCS) and by the E-rosette technique using sheep red blood cells (SRBC). This approach reveals a new means of dissecting the immunodeficiency diseases before BMT and a method for assessing cellular reconstitution after marrow transplantation.

Zinc deficient humans and animals have depressed thymic mass and increased susceptibility to infection. In the present studies, we investigated the relationship between cellular immunity, thymic hormones, and serum zinc levels in 19 patients with common varied immunodeficiency. Five (26%) had serum zinc levels 2 SD below normal and 11 (58%) had abnormally low lymphocyte proliferation to at least one mitogen. A significant statistical correlation between zinc levels and lymphocyte proliferation to phytohemagglutinin and concanavalin A was identified. Forty-two percent had abnormally low levels of facteur thymique serique and 74% had low levels of thymopoietin, although no statistical relationship between the levels of these hormones, zinc levels, or lymphocyte proliferation could be identified. Three patients with the most profound zinc deficiency had substantial increases in thymic hormones after zinc repletion, and two had complete resolution of intractable diarrhea. A therapeutic potential of zinc for certain patients with hypogammaglobulinemia is suggested.

Transplantation of two fetal thymuses failed to reconstitute the immune function in a patient with the DiGeorge syndrome. Serum thymic hormones (facteur thymique serique and thymopoietin), which had been nondetectable, became normal after thymus transplantation. Studies done on the patient's fractionated bone marrow cells in vitro appeared to reflect defective capacity for T-lymphocyte differentiation. In spite of the efforts at treatment, the child died at 2 years of age, apparently due to an associated cardiovascular abnormality. At autopsy, no thymic tissue could be found. Failure of immunologic reconstitution after fetal thymus transplantation in this patient with the DiGeorge syndrome may have resulted from deficiencies of precursor cells.