The overall efficiency of derivation of iPS cells by transcription factor overexpression is low (0.01% to approximately 6% of the treated cells) [11,12,20,21], but can be increased by various means, including noncoding RNAs, culture conditions, and so on. Transcription factor overexpression induces iPS cells approximately 20 times less often when immature T cells are compared to thymic progenitor cells, and approximately 300 times less efficiently when mature peripheral T cells are compared to thymic progenitors (Figure 2e) [22].
