Cells in spontaneous DNA synthesis in cord blood of premature and full-term newborn infants. An autoradiographic study.

Cord blood from 16 premature infants and 10 full-term infants, and blood from 10 healthy adults, was incubated for 30 minutes with tritiated thymidine, after which an autoradiographic study was made of spontaneously labeling cells. Apart from a varying number of erythroblasts, myelocytes, and an occasional blast cell, two main types of spontaneously labeling cells were observed: transitional cells and large lymphoid cells, previously shown to be phagocytic. Spontaneously labeling cells were 12 times more frequent in cord blood of premature and full-term infants than in the blood of adults. No transitional cells were seen in adult blood.