Abstract
1. It has been demonstrated that human peripheral lymphocytes can be adequately maintained in long-term culture, in a viable state, by the incorporation of a subthreshold concentration of phytohemagglutinin into the medium and changing the medium every 7 days.
2. These cells, after 42 days of culture, are capable of undergoing blastogenesis and mitosis upon incubation with blastogenic doses of phytohemagglutinin.
3. The morphology of these stimulated cells, and the degree of incorporation of isotope, attests to the healthy state of these cells.
4. Cells incubated for 42 days in the presence of a subthreshold concentration of PHA are capable of incorporating three to four times the amount of tritiated thymidine as can cells incubated for 42 days in medium without the subthreshold concentration of PHA.
