Sex as a confounding factor in the effects of ageing on rat lymph node t cell compartment

The study examined the influence of sex on the alterations occurring with ageing in rat lymph node (LN) T cell compartment. In female and male rats the decrease in LN T cell counts was followed by a shift in CD4+/CD8+ T cell ratio towards CD8+ T cells, which was more prominent in males than in females. With ageing, in both major LN T cell subpopulations naive (recent thymic emigrants and mature naive cells) to memory/activated T cell ratio shifted to the side of memory/activated cells in female, and particularly in male rats. The frequency of regulatory CD25+Foxp3+ cells increased among LN CD4+/CD8+ T cells with ageing, reflecting, at least partly, an enhanced conversion of effector T cells into regulatory cells. This was also more prominent in male rats. The more prounounced increase in LN oxidative damage and the expression levels of proinflammatory cytokines in male rats with ageing, most likely contributed to the greater frequency of proinflammatory, replicatively senescent CD28- cells expressing CD11b (innate cell marker), among T cells of old male rats compared with age matched females. The increase in LN oxidation/proinflammatory state with ageing was also consistent with the accumulation of exhausted PD-1(high) cells among T lymphocytes, particularly prominent among CD8+ T cells from male rats. Finally, by calculating a summary score for the key ageing-relevant parameters (an ageing index), a faster development of the deleterious changes in the T cell compartment occurring with ageing was confirmed in male rat LNs. Additionally, the study pointed to indices of LN T cell compartment ageing which correlate with those in peripheral blood.