The Possible Involvement of Apoptotic Decay of Terminal Deoxynucleotidyl Transferase-Positive Lymphocytes in the Reutilization of the Extracellular DNA Fragments by Surrounding Living Cells

The migrating TdT+ thymocytes can die in other tissues, promoting the surrounding cells’ renewing likes holocrine secretion does. To clarify the role of TdT-enzyme for this function of progenitor lymphocytes, their extracellular media with its components included by living cells analyzed in vitro before and after in vivo irradiation of donor rats. The nucleoid with DNase-sensitive (free) DNA and TdT activity discovered in extracellular media conditioned preliminary by spontaneous apoptotic death of a minor part of the thymocyte’s suspension in vitro. The penetration of labeled products of non-template synthesis with free DNA’ primers from media into cells by pinocytosis confirmed by exogenous polymeric DNA marked artificially. The DNA penetration into cells follows an increase of the cell’s viability and acceleration of spontaneous intracellular DNA-synthesis controlled with labeled thymidine uptake. Both phenomena are typical for either the lowest initial concentration of intact cells or their preliminary irradiation in vivo. The data point to possible involvement of apoptotic decay of TdT+ cells in the reutilization of the extracellular DNA fragments for reparation/regeneration of surrounding living cells.