Investigations of the induction period of an in vitro hemolysin response to sheep erythrocyte antigen revealed the following:

1. After antigen stimulation precursors of plaque-forming cells rapidly maturate to the point of hemolysin production.

2. Initial maturation probably occurs in the absence of cell division.

3. After initial maturation, a latent period of about 12 hr occurs before the first doubling of PFC.

4. At least the first three cell doublings are synchronous, with a generation time of 7–8 hr.

5. Synchronous cell division implies that all precursor cells are at the same point in the cell cyde when they are initially stimulated.

This content is only available as a PDF.