OBJECTIVE To explore the relationship between the clinical characteristics of acoustic neuroma and the number ofT lymphocytes in tumor tissues.METHODS Clinical data of 65 patients diagnosed with VS were retrospectively collected.Peripheral blood samples of the patients were collected and the number of T lymphocytes were counted by flow cytometry.Immunohistochemistry was carried out with the fresh tumor samples compared with 8 normal cranial nerve controls.The expression level of each immune protein was analyzed its correlation with clinical characters was explored.RESULTS The CD3+,CD4+ and CD8+ T lymphocytes in the peripheral blood are not significantly correlated with clinical data.In the tumor tissues,the number of CD4+ and CD8+ T lymphocytes are much larger than those in normal cranial nerves,and negatively correlated with preoperative hearing.The number of CD8+ T lymphocytes has a negative relationship with postoperative facial nerve function.In addition,CD4 and CD8 expression levels in the tumor samples from patients younger than 40 are much higher than those in elder patients.Foxp3 is not detected in the normal cranial nerves.The number of Foxp3+ T lymphocytes is negatively correlated with preoperative hearing.CONCLUSION The CD4+ and CD8+ T lymphocytes mediated cellular immunity play an important role in the development of acoustic neuroma,as well as the reservation and restoration of nerve function.