Variability of results of lymphocyte transformation assays in normal human volunteers. Responses of mononuclear leukocytes to mitogen stimulation.

Human mononuclear leukocyte transformation responses were tested in a microassay system using measurement of tritiated thymidine incorporation stimulated by different mitogens. A wide range of results was found using cells isolated by Ficoll-Hypaque separation of blood from normal volunteer donors. Considerable variation was seen in the responses of different individuals tested concurrently, and in the responses of single individuals tested sequentially. Wide variation in responses existed even when dose-response curves were produced. There was little variation in the cell concentrations or mitogen concentrations that produced optimal responses in this assay. Caution in comparing responses of mononuclear leukocytes obtained at different venipunctures is advised.