Abstract: Objective To explore the role of CD4+CD25+ regulatory T cells (Treg) in the occurrecne of spontaneous subarachnoid
hemorrhage (SAH). Methods Fifteen patients with spontaneous SAH, 15 with traumatic SAH, and 15 with headache without
organic pathologies as confirmed by lumbar puncture (control group) were examined with flow cytometry for Treg in the
peripheral blood and cerebrospinal fluid and intracellular cytokine interleukin-10 (IL-10) and transforming growth factor beta1
(TGF-β1) levels. The Glasgow score (GCS), neurological deficit score (NIHSS), headache, visual analog scale (VAS) and
hospitalization time were compared between the two SAH groups. Results Spontaneous SAH patients showed significantly
lowered peripheral blood Treg, IL-10, and TGF-β1 in the cerebrospinal fluid compared with the patients with traumatic SAH
and the control group (P<0.05), and the 3 measurements were comparable between the latter two groups (P>0.05). After
administration of treatment, of Treg content in spontaneous SAH patients increased progressively and became comparable
with those in the other two groups at the third and fourth lumbar punctures. Spontaneous SAH patients showed significantly
lower GCS, NIHSS, and VAS with shorter hospital stay than the traumatic SAH patients. Correlation analysis showed that
Treg, IL-10 and TGF-β1 were all inversely correlated with NIHSS, VAS, and duration of hospitalization but positively
correlated with GCS (the absolute r values were all greater than 0.6, P<0.05). Conclusion Treg deficiency can be an important
mechanism for the occurrence of spontaneous SAH, and a higher level of Treg indicates a better outcome of the patients.