Human telomerase consists of two essential components, telomerase RNA template (hTER) and telomerase reverse transcriptase (hTERT), and functions to synthesize telomere repeats that serve to protect the integrity of chromosomes and to prolong the replicative life span of cells. Telomerase activity is expressed selectively in germ-line and malignant tumor cells but not in most normal human somatic cells. As a notable exception, telomerase is expressed in human lymphocytes during development, differentiation, and activation. Recent studies have suggested that regulation of telomerase is determined by transcription of hTERT but not hTER. The highly regulated expression of telomerase in lymphocytes provides an opportunity to analyze the contribution of transcriptional regulation of hTERT and hTER. We report here an analysis of hTERT expression by Northern and in situ hybridization. It was found that hTERT mRNA is expressed at detectable levels in all subsets of human lymphocytes isolated from thymus, tonsil, and peripheral blood, regardless of the status of telomerase activity. hTERT expression is regulated as a function of lineage development, differentiation, and activation. Strikingly, however, telomerase activity in these cells is not correlated strictly with the levels of hTERT and hTER transcripts. The absence of correlation between telomerase activity and hTERT mRNA could not be attributed to the presence of hTERT splice variants or to detectable inhibitors of telomerase activity. Thus, transcriptional regulation of hTERT is not sufficient to account for telomerase activity in human lymphocytes, indicating a likely role of posttranscriptional factors in the control of enzyme function.

The superior sensitivity and specificity associated with the use of molecular assays has greatly improved the field of infectious disease diagnostics by providing clinicians with results that are both accurate and rapidly obtained. Herein, we review molecularly based infectious disease diagnostic tests that are Food and Drug Administration approved or cleared and commercially available in the United States as of December 31, 2010. We describe specific assays and their performance, as stated in the Food and Drug Administration's Summary of Safety and Effectiveness Data or the Office of In Vitro Diagnostic Device Evaluation and Safety's decision summaries, product inserts, or peer-reviewed literature. We summarize indications for testing, limitations, and challenges related to implementation in a clinical laboratory setting for a wide variety of common pathogens. The information presented in this review will be particularly useful for laboratories that plan to implement or expand their molecular offerings in the near term.