Programme Hospitalier Recherche Clinique, Institut Pasteur, Inserm, French Public Health Agency.

Reduced thymopoiesis and continuous mobilization of naive T cells into the effector–memory pool can lead to severe alterations of the naive T cell compartment. However, maintenance of the naive T cell population is essential to mount effective immune responses. Evidence of homeostatic regulation of naive T cells is currently debated in animal models. In humans, the situation remains unresolved, in particular with advanced age. In this study, we analyzed the CD4+ and CD8+ naive T cell compartments from elderly, young adults thymectomized during early childhood, and HIV-1–infected patients, which are characterized by T lymphocytopenia. We show a direct association between increased turnover and decreased frequency of naive T cells. Moreover, the IL-7–induced pathway was fully functional in naive T cells from elderly and young adults thymectomized during early childhood, who are characterized by elevated IL-7 plasma levels. Our findings support the establishment of homeostatic regulation of naive T cell proliferation in humans. This regulation is particularly active in lymphopenic hosts, such as elderly and thymectomized patients.

γδ T cells represent a subset of unconventional T lymphocytes that are known for their reactivity against different pathogens and considered as intermediate mediators between adaptive and innate immunity. We provide in this paper further insights underlying the changes that affect the γδ T cell compartment with advanced age in humans. We show that both aging and CMV infection impact independently on the γδ T cell compartment. Most γδ T cells are significantly affected by age and present a decreased frequency in the elderly. The decline of the γδ T cell pool appears to be independent from the activity of the thymus, arguing in favor of an extrathymic site of γδ T cell production in humans. Of note, CMV infection, which is directly associated with the activation of the pool of Vδ2− γδ T cells, promotes nonetheless the inflation of this compartment throughout life. CMV seropositivity accentuates further the accumulation of highly differentiated lymphocytes in Vδ2− γδ T cell subsets with time, in contrast to Vδ2+ γδ T cells, which maintain a less differentiated phenotype. This is similar to the effect of CMV on αβ T cells and suggests that γδ T cells may vary in differentiation phenotype according to distinct stimuli or pathogens.

BPRO exhibits significant within-day variability in elderly patients. Within-day and day-to-day reproducibility of the diagnosis of OH, based on conventional criteria, were found to be poor.

OBJECTIVE: To study the regulation of antidiuretic hormone (ADH) and atrial natriuretic peptide (ANP) in obese and lean women with a swelling syndrome. PATIENTS: Thirty-four obese women and 12 lean women with a swelling syndrome and an abnormal isotopic test of capillary permeability to albumin were investigated. MEASUREMENTS: After 10 nocturnal hours of¯uid restriction, subjects were asked at 8 am to ingest a tap water load of 20 ml/kg within 10 min and to remain strictly recumbent until twelve noon on the ®rst day, and to remain standing and to walk around until twelve noon on the second day. Free water clearance and the cGMP/creatinine and albumin/ creatinine ratios were determined hourly in the morning. RESULTS: The total 4 h-urinary volume/ingested water volume ratio was signi®cantly lower on the second day both in the lean and the obese patients, the differences being slightly larger in the obese patients. The increase in free water clearance was signi®cantly less on the second day in the obese patients. The increase in cGMP/creatinine ratio was also signi®cantly lower on the second day in the obese patients. The maximum level of the urinary albumin/creatinine ratio was signi®cantly higher on the second day in the obese patients. CONCLUSION: In obese women with a swelling syndrome: (1) The higher increase in the urinary albumin excretion rate after water loading followed by a sustained upright position suggests a widespread alteration in capillary function, which is also indicated by the isotopic test of capillary permeability to albumin. (2) The water load-induced inhibition of ADH secretion and stimulation of ANP secretion or ANP activity, more defective in the upright position than in the recumbent one, is probably another major contributing factor to orthostatic oedema.