The Mechanismof 67GaAssociationwith Lymphocytes1

SUMMARY Human thymus-dependent lymphocytes cultured in vitro were used as a model to study mechanisms of 67Ga uptake. Lymphocyte affinity for 67Ga was studied in unstimulated cells and cells stimulated by phytohemagglutinin. The evidence suggests that 67Ga uptake is linear as a function of 67Ga concentration in both stimulated and unstimulated cells and that 67Ga associates primarily and tenaciously with the plasma membranes of lymphocytes. In addition, increased 67Ga uptake seen in phytohemagglutinin-stimulated cells appears to be associated with changes in the plasma membrane.