Optimal conditions for polyclonal antibody secretion and DNA synthesis in human blood and spleen lymphocytes by lipopolysaccharide.

Lipopolysaccharides from E. coli (LPS) stimulated increased DNA synthesis and high-rate antibody secretion in human lymphocytes from blood and spleen. Peak DNA synthesis by 10 or 100 microgram/ml LPS was seen on day 6 for blood lymphocytes. Using 500 microgram/ml of LPS the peak response was reached on day 5 and with 0.1--1 microgram/ml the maximal stimulation was on day 7. For spleen cells LPS 100 microgram/ml gave a peak stimulation on day 4 or 5. Antibody secretion, measured as plaque-forming cells (PFC) against fluorescein isothiocyanate-coupled sheep erythrocytes in a haemolysis-in-gel assay, was maximal on day 5 in blood lymphocytes and on day 3 or 4 in spleen cells. The highest cell viability and antibody secretion after stimulation with LPS was obtained in 16 mm diameter multiwell plates usng 2.5 x 10(6) cells in 1 ml of medium containing 10% AB serum absorbed with SRBC. Feeding of cultures was essential for stimulation of blood lymphocytes but not for spleen cells.