Early events during the activation of human lymphocytes by the mitogenic monoclonal antibody OKT3.

The effects of the mitogenic monoclonal antibody OKT3 on the metabolic changes preceding DNA synthesis during the activation of human peripheral blood mononuclear cells were compared with those induced by PHA. The aspects studied included uridine transport, the incorporation of inositol into phospholipids, Na+-dependent amino acid uptake, and protein synthesis. All four parameters were increased in response to the ligation of the T lymphocyte receptor recognized by OKT3. These changes were apparent as early as the corresponding changes induced by PHA. However, the increases in uridine uptake and inositol incorporation were disproportionately reduced when compared to those caused by PHA, and no evidence of high-dose inhibition was seen in cells activated by OKT3. This suggests that at least some lectin-induced changes in metabolism are mediated through additional mechanisms, probably involving distinct receptors.