On the importance of substrate adhesion and cell aggregation in the Con A-induced blastogenesis of lymphocytes

The importance of substrate adhesion and cell aggregation for the Con A-induced blastogenesis of human peripheral lymphocytes was studied by flow cytometric methods. The percentage of lymphocytes responding to the mitogen by growth and DNA synthesis was approximately the same among non-adherent, single cells as among substrate-adherent and aggregated cells. However, the response of the former cells was delayed by about 10 h as compared with that of adherent and aggregated cells. This delay increased to about 20 h in monocyte-depleted cultures. Stimulation with succinyl-Con A, which caused negligible aggregation, produced a significant response. Blast cells appeared to be largely non-adherent. It is concluded that neither substrate adhesion nor cell aggregation are prerequisites for Con A-induced blastogenesis, although substrate adhesion seems to have a significant promotive effect that is probably associated with a direct contact of the lymphocytes with monocytes.