Mind the cell: Seasonal variation in telomere length mirrors changes in leukocyte profile.

Leukocytes are typically considered as a whole in studies examining telomere dynamics in mammals. Such an approach may be precarious, as leukocytes represent the only nucleated blood cells in mammals, their composition varies temporally, and telomere length differs between leukocyte types. To highlight this limitation, we examined here whether seasonal variation in leukocyte composition was related to variation in telomere length in free-ranging mandrills (Mandrilllus sphinx). We found that the leukocyte profile of mandrills varied seasonally, with lower lymphocyte proportion being observed during the long dry season presumably because of the combined effects of high nematode infection and stress at that time of the year. Interestingly, this low lymphocyte proportion during the long dry season was associated with shorter telomeres. Accordingly, based on longitudinal data, we found that seasonal changes in lymphocyte proportion were reflected by corresponding seasonal variation in telomere length. Overall, these results suggest that variation in lymphocyte proportion in blood can significantly affect telomere measurements in mammals. However, lymphocyte proportion did not entirely explain variation in telomere length. For instance, a lower lymphocyte proportion with age could not fully explain shorter telomeres in older individuals. Overall, our results show that telomere length and leukocyte profile are strongly although imperfectly intertwined, which may obscure the relationship between telomere dynamics and aging processes in mammals. This article is protected by copyright. All rights reserved.

This article is protected by copyright. All rights reserved.

KEYWORDS: infection; leukocytes; primates; seasonality; stress; telomeres

PMID: 28817217 DOI: 10.1111/mec.14329