Attempt to restore lymphocytes with defective T-cell function by mixing with normal cells in vitro.

Blood leukocytes from a patient with T-cell immunodeficiency failed to respond to stimulation with phytohemagglutinin (PHA) in vitro although ample lymphocytes were present. Leukocytes from this patient were mixed in various proportions with normal leukocytes, and the mixtures were stimulated with PHA and cultured for three days. There was no restoration of PHA responsiveness of the patient's cells in the presence of normal cells. This would indicate that the defect in the patient's cell population was not due to the absence of any facilitating factor or cooperative function that could be provided by normal T cells or other blood leukocytes. Since in thymic aplasia the patient's own cells are rapidly restored to normal PHA responsiveness by an unknown facilitating factor after thymic transplantation, we suggest that this mixed-cell culture method might differentiate between patients who need a bone marrow transplant and those who will respond to a thymus transplant.