Influence of erythrocyte contamination on the optimal phytohaemagglutinin concentration in Chinese hamster lymphocyte cultures.

Lymphocyte cultures from the Chinese hamster were made with lymphocytes isolated with Ficoll-Isopaque or with Haemaccel. In some experiments the red blood cells (r.b.c.) that remained after lymphocyte isolation were lysed. Optimum phytohaemagglutinin (PHA) concentration for lymphocyte proliferation depended upon the manner in which the lymphocytes were obtained. Lower PHA concentrations were needed for optimum stimulation of lymphocytes isolated with Ficoll-Isopaque than for lymphocytes isolated with Haemaccel. Lysis of the r.b.c. remaining after isolation of lymphocytes with Haemaccel resulted in a decrease of optimum PHA concentration. The optimum PHA concentration depended strongly on r.b.c. contamination, the higher the r.b.c. contamination the higher the optimum PHA concentration. However, only part of the differences found in optimum PHA concentrations can be attributed to r.b.c. contamination.