Activation of purified human thymus-derived (T) cells by mitogens. II. Monocyte- macrophage potentiation of mitogen-induced DNA synthesis.

Thymus-derived (T) cells from peripheral blood were purified by rosette formation with neuraminidase-treated sheep red blood cells (SRBC) and centifugation on Ficoll-Hypaque. T cells recovered from the pellet were freed of SRBC by treatment with Tris-NH4Cl. T cells purified by this method showed a diminished ability to take up 3H-thymidine (3H-TdR) after mitogen stimulation when compared to the mitogenic response of an equal number of autologous peripheral blood mononuclear lymphocytes (PBL). Autologous monocytes restored the capacity of purified T cells to take up 3H-TdR in the presence of phytohemagglutinin (PHA) or Concanavalin A (Con A). The effect was proportional to the number of monocytes added. Similar restorative effects could be obtained with allogeneic or xenogeneic monocytes. These data suggest that the mitogenic stimulation of human PBL and Con A may reflect the participation of more than one cell type: the T cells and monocyte and that the genetic origin of the monocyte is not critical for augmentation of the mitogenic activation of human T cells.