Studies on human peripheral blood lymphocytes in vitro. 3. Fine structural features of lymphocyte transformation by pokeweed mitogen.

Summary 1 )Pokeweed mitogen (PWM)-stimulated cells show maximum transformation after 72 hr in culture. When optimal concentrations of PWM are used, the transformed cells do not exceed 50 to 60% of the total. 2 )After 72 hr the population of cells includes small and medium-size lymphocytes, large phytohemagglutinin (PHA)-like blast cells and a unique intermediate sized cell type. 3 )The intermediate sized PWM cell is characterized by an eccentric nucleus with clumped heterochromatin, a well developed Golgi apparatus, ribosomal aggregates and a well developed rough-surfaced endoplasmic reticulum. The fine structural features differ importantly from those consistently seen in PHA transformed cells. 4 )The possible immunologic significance of PWM stimulation of human peripheral lymphocytes in vitro has been considered.