CD34 and central nervous system cancer: Phase I clinical trial of IFNB gene therapy for glioma. In histological examinations of autopsy samples many tumor cells showed necrotic changes, and immunohistochemistry identified numerous CD8+ lymphocytes and macrophages infiltrating the tumor and surrounding tissues, while CD34-immunoreactive vessels were notably decreased in the vector-injected brain (Wakabayashi et al., 2008).