Mechanisms of Ageing and Development 121 (2000) 59–67 A simple method for the measurement of sjTREC levels in blood Richard Aspinall *, Jeff Pido, Deborah Andrew Department of Immunology, Imperial College School of Medicine, Chelsea and Westminister Hospital, 369 Fulham Road, London SW 10 9NH, UK Received 2 July 2000; received in revised form 21 July 2000; accepted 30 July 2000 Abstract We have developed a relatively rapid, safe and simple method for the quantification of sjTREC levels in samples of peripheral blood. The assay uses an image analysis package to measure the brightness of PCR product bands on an image of the standard agarose gel. Comparison of the brightness of the band with that obtained from a standard curve provides a read-out of the amount of sjTRECs in the sample. We have compared the sjTREC levels we obtained with this method with those obtained from real time analysis PCR using a Lightcycler and found that they are comparable. © 2000 Elsevier Science Ireland Ltd. All rights reserved. Keywords: sjTREC; Thymic output; PCR www.elsevier.com/locate/mechagedev 1. Introduction Extrapolation of the rate of loss of thymic tissue in humans suggests that it would be completely absent by the time the individual reaches the age of 120 years (Steinmann, 1986). Loss of thymic tissue over this period is not uniform but more likely biphasic with a period of rapid loss preceding middle age followed by a period of relatively slow tissue loss calculated by some to be less than 1% per year (Steinmann, 1986; Kendall et al., 1980; Bertho et al., 1997). In addition to the loss of thymopoetically active tissue there is the gradual deposition of fat within the * Corresponding author. Tel.: +44-20-87465993; fax: +44-20-87465997. E-mail address: r.aspinall@ic.ac.uk (R. Aspinall). 0047-6374/00/$ - see front matter © 2000 Elsevier Science Ireland Ltd. All rights reserved. PII:S0047-6374(00)00197-4