Expression of transcription proteins PAX1, Hoxa3, and TLP regulating differentiation of thymic epithelial cells is detected in human thymus starting from gestation week 22 until the age of 95 years. Expression of transcription factors significantly decreased during aging. Apart from the decrease in the expression of signal differentiation factors in cultured thymic epithelial cells, proliferative activity of T lymphocytes cocultured with thymic epithelial cells also decreased in aging cultures, which demonstrated the important regulatory effect of transcription proteins on maturation and maintenance of T lymphocytes. Taking into account the important role of transcription proteins in the regulation of proliferation and function of T lymphocytes, whose number sharply decreases during aging, the maintenance of the level of expression of transcription factors during aging is a promising trend in modern biogerontology.