Colony formation by human T lymphocytes in agar medium

An improved method is described for growing human T-lymphocyte colonies in agar medium containing phytohaemagglutinin (PHA) and sheep red blood cells (SRBC). Cluster and colony growth was obtained when blood mononuclear cells were plated directly in the agar-medium (one-step procedure) or after incubation of cells in liquid medium with PHA (two-step procedure). In the one-step procedure approximately 1 per 100 cells plated formed a cluster containing four to fifty cells. In the two-step procedure 1 per 20 cells plated formed a cluster or a colony (more than fifty cells). The proliferating cells were shown to be sheep-erythrocyte rosette-forming cells (E-RFC). Optimal proliferation was dependent on the presence of phagocytic cells in the cell suspensions cultured. No growth occurred in cultures depleted of E-RFC. Detailed studies of the cycle, velocity sedimentation, and density of the cells plated showed that the majority of cluster- and colony-forming cells were small non-cycline lymphocytes with a sedimentation velocity of 4 mm/hr, and a density between 1-069 and 1-077 g/cm3.