The Activation of Fetal Lymphocytes

Abstract

Fetal lymphocytes from the cord blood of normal full‐term fetuses can be stimulated in vitro by PHA to transformation and mitotic division. The reaction kinetics differ from those of adult cells, in that the minimum G1 period is about 4 h shorter. However, the cord blood also contains a small number of lymphocytes, which enter the S period very soon after the addition of PHA, i.e. they have been prestimulated in vivo. These cells are completely lacking in adult blood. In addition, fetal lymphocytes show a significantly higher spontaneous transformation ratio. Possible reasons for these differences are discussed.