Human lymphocyte colony formation: a comparison of stimulation with intact staphylococcus, staph, protein A, pokeweed mitogen and phytohemagglutinin.

The efficacy of various mitogens for growing human lymphocyte colonies in semisolid agar cultures was tested. Protein A as well as phytohemagglutinin (PHA) exhibited a strong stimulatory capacity in contrast to Cowan I strain of Staphylococcus aureus (Cowan I). Pokeweed mitogen (PWM) was effective and generated a sizeable number of colonies. Plating efficiency of lymphocytes from different donors and for the same donors cultured on different days were highly variable. Regardless of mitogen, colonies grew predominantly on the upper and lower surfaces of the agar and these were predominantly composed of T lymphocytes. A much smaller number of colonies grew within the agar and these were found to be monocytes or a mixture of monocytes granulocytes. Under chosen concentrations of agar and mitogens, dose responses of colony number per number of cultured cells were determined. These were found to be characteristic for each of the mitogens but none were linear. The possibility of cell-cell interactions being important for proliferation is therefore raised.