Guillermo B. Semeniuk

Bilateral Carotid Body Paraganglioma and Central Alveolar Hypoventilation

A 62-year-old woman with a bilateral carotid body paraganglioma presented, 2 years after the removal of the right one, with signs of right-heart failure. Hypoxemia, hypercapnia, polycythemia and pulmonary hypertension with normal ventilatory capacity were found. Central alveolar hypoventilation was diagnosed on the basis of absence of ventilatory response and sensation to provoked hypercapnia, prolonged breath-holding time and correction of hypercapnia by voluntary hyperventilation.

Identification and Clinical Relevance of Naturally Occurring Human CD8+HLA-DR+ Regulatory T Cells

The lack of responsiveness to self and non-self Ags is normally maintained by multiple mechanisms, including the suppressive activities of several T cell subsets. In this study, we show that CD8+ T cells from both adult peripheral blood and umbilical cord blood mononuclear cells constitutively expressing HLA-DR represent a natural human CD8+ regulatory T cell subset. Their suppressive effect appears to be cell-to-cell contact dependent and may involve CTLA-4 signaling between neighboring T cells. These regulatory T cells can be expanded in vitro and exhibit a suppressive capacity similar to that observed in ex vivo CD8+HLA-DR+ T cells. The high frequency of CD8+HLA-DR+ T cells that we detected in patients with non–small cell lung cancer deserves further work to confirm their putative suppressor effect within the tumor.