Volume 59 (2009) Issue: 2009 No#1

Peripubertal ovariectomy provides long-term postponement of age - associated decline in thymic cellularity and T-cell output

Author(s): Perišić Milica, Kosec D, Pilipović I, Radojević Katarina, Pešić Vesna, Rakin Ana, Leposavić Gordana

Keywords:ovariectomy, ageing, thymic cellularity, recent thymic emigrants

The present study was undertaken to reassess the recently challenged role of ovarian hormones in age-associated thymic involution. For this purpose, in eleven-month-old peripubertally ovariectomized (Ox) rats we analyzed: i) thymic weight and cellularity, ii) size of CD4+CD8+ double-positive (DP) thymocyte population, which is believed to correlate to the thymic capacity to export mature T cells, iii) number of recent thymic emigrants (RTEs), and iv) number of peripheral blood CD4+ and CD8+ lymphocytes. It was found that both thymic weight and cellularity were greater in Ox than in control rats. In addition, in Ox rats the numbers of DP thymocytes and both CD4+ and CD8+ RTEs, were significantly greater than in controls, indicating a more efficient generation of T cells in these rats. Furthermore, these findings, coupled with data indicating that the number of neither CD4+ nor CD8+ peripheral blood lymphocytes was affected by ovariectomy, most likely, suggest a reduced homeostatic proliferation of memory cells in Ox rats, i.e. broadening of TCR peripheral repertoire without changes in the overall number of T cells leading to a more efficient response to newly encountered antigens. The results indicate that the ovarian steroid deprivation from early peripubertal period leads to a long lasting postponement/alleviation of age-associated decline in Tcell mediated immune response.