[Age-related effects in thymocytes differentiation: role of pineal gland peptide factors].

The peculiarities of the differentiation of the thymocytes in adult and old CBA/Ca mice were studied with a help of the monoclonal antibodies to different lymphoid antigens of mice. In the thymus of old mice, the portions of the CD4-CD8-, CD44+ and CD44+Thy-1(-)-cells have been shown to be increased. The percentage of the CD4+CD8(+)-thymocytes did not change, whereas the portion of CD25+, PNA+, CD3+, CD3+CD8+, CD4+CD8- and CD4-CD8(+)-cells diminished. The ratios of different subpopulations of thymocytes, characterizing different degree of their maturation are changing with age towards the prevalence of less mature cells. After prolonged (for 18 months) administration of epithalamine the portion of CD44+, CD44+Thy-1- and CD3- 8(+)-cells in the old thymus has been shown to be decreased, while that of CD25+, CD3+, CD3+CD8+, CD4+CD8/and CD4-CD8(+)-cells increased. According to many parametres thymus of those old animals corresponds to adult mice. Epithalamine raised the titer of one of the thymic hormones--thymic serum factor, both in the blood of the old mice and in the supernatant of a 3-hour culture of the thymic stroma.