The control of immune response in vitro by Ca2+. II. The Ca2+-dependent period during mitogenic stimulation

The Ca2+ requirement for stimulation of DNA synthesis in vitro by phytohaemagglutinin (PHA) and by lipopolysaccharide (LPS) was investigated using mouse spleen cells. During mitogenic stimulation two periods could be distinguished: a Ca2+-independent period which was followed by a Ca2+-dependent period. The results suggest that Ca2+ is required for a step preceeding DNA synthesis but not for the early initial phase of transformation.