Measurement of subgroups of peripheral blood T lymphocytes in patients with severe acute respiratory syndrome and its clinical significance.

To investigate the changes of subgroups of peripheral blood T lymphocytes in patients with severe acute respiratory syndrome (SARS) and its clinical significance.Subgroups of blood T lymphocytes in 93 patients with SARS were detected by flow cytometer. The results detected in 64 normal subjects and 50 patients with AIDS served as controls.The numbers of CD(3)(+), CD(4)(+), and CD(8)(+) lymphocytes all significantly decreased in acute phase of patients with SARS [(722 +/- 533)/microliter, (438 +/- 353)/microliter, (307 +/- 217)/microliter] compared with those in normal controls [(1527 +/- 470)/microliter, (787 +/- 257)/microliter, (633 +/- 280)/microliter, all P <0.01], which was different from what we observed in patients with AIDS who had decreased CD(4)(+) [(296 +/- 298)/microliter] but increased CD(8)(+) [(818 +/- 566)/microliter] counts. The counts of CD(3)(+), CD(4)(+), and CD(8)(+) lymphocytes decreased more apparently in patients with severe SARS. All the five patients who died had CD(4)(+) counts less than 200/microliter. As the patients' condition improved, CD(3)(+), CD(4)(+), and CD(8)(+) counts gradually returned to normal ranges.The damage of cellular immunity is probably an important mechanism of pathogenesis of SARS.