Effect of thymus factor on human precursor T lymphocytes

A pig thymus factor is shown to transform in vitro human immature lymphoid cells (from cord blood, bone marrow and foetal tissue) into mature T lymphocytes forming spontaneous rosettes with sheep erythrocytes. No effect was observed on normal mature lymphocytes (T or B cells), suggesting a selective activity of the thymus factor for precursor T lymphocytes. When lymphocytes from various patients were treated with the thymus factor, the most pronounced effect was found on cells from T cell-deficient patients. This finding suggests that these patients were lacking such a humoral thymus factor and were not genuinely deficient in their lymphocytes. Our results indicate a potential diagnostic value of the thymus factor, especially in the analysis of immunodeficiency diseases.