Recent Thymic Emigrants Do Not Account for the Increased Number of TCells Seen in the Lungs of Stable Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) patients have an increased number of T cells within their lungs.It is unknown whether these T cells, remain there forever or if there is a continuous turnover from the blood.In the adult, there is a significant T lymphocytopoiesis from the thymus producing cells known as recent thymic emigrants (RTEs).T cell receptor excision circles (TREC) are a marker of RTEs.We investigated the number of TREC in blood from patients with untreated stable, mild to moderate COPD (n=6) compared with age-matched smokers with normal lung function (n=6) and nonsmokers (n=8).The results showed variable expression of TREC in each subject group and no significant difference between TREC expressions in any group of subjects.Changes in T-cell numbers in the lung of stable COPD patients may reflect prolonged survival or proliferation of these cells within the lung rather than continuous recruitment from the blood.