Abstract
Telomerase activity is not readily detected in resting human T lymphocytes, however upon antigen presentation, telomerase is transiently upregulated. Presently, it is not known if telomerase activation is necessary for the proliferation of T cells or for the maintenance of telomere lengths. In this study, we found that telomerase activation is not required for the short- term proliferation of T cells and that telomeres progressively shorten in a heterogeneous population of T cells, even if telomerase is detected. By measuring telomerase activity at the single-cell level using quantitative ddPCR techniques (ddTRAP) and by monitoring changes in the shortest telomeres with more sensitive telomere length measurement assays, we show that only a subset of CD28+ T-cells have robust telomerase activity upon stimulation and are capable of maintaining their telomere lengths during induced proliferation. The study of this T-cell subset may lead to a better understanding on how telomerase is regulated and functions in immune cells.
Highlights
It is known that upon mitogen stimulation, immune cells can be activated and divide rapidly
By taking advantage of novel techniques that can measure telomerase activity at the single-cell level using quantitative ddPCR techniques[16] and by monitoring subtle telomere changes using limited DNA input and more sensitive telomere length measurement assays, in this report we show that only a subset of CD28+ T-cells show robust telomerase activity upon stimulation
There are a variety of methods that can achieve similar outcomes for in vitro T cell stimulation, including concanavalin A (ConA)[17], phytohaemagglutinin (PHA)[8, 18], phorbol 12-myristate 13-acetate (PMA)/ ionomycin[18], and anti-CD3/CD28
Summary
It is known that upon mitogen stimulation, immune cells can be activated and divide rapidly. By taking advantage of novel techniques that can measure telomerase activity at the single-cell level using quantitative ddPCR techniques (ddTRAP)[16] and by monitoring subtle telomere changes using limited DNA input and more sensitive telomere length measurement assays, in this report we show that only a subset of CD28+ T-cells show robust telomerase activity upon stimulation. This subset of T-cells appear to be capable of maintaining their telomere lengths whereasCD28- cells have significantly more short telomeres, even though they proliferate at similar rates compared to CD28+ cells. Investigating the function of telomerase activation during T cell stimulation may provide new insights into understanding normal immune responses (T cell in vivo proliferation), as well as T cell ex vivo expansion, which is a critical requirement for recent immunotherapy protocols
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