CTLA4 and neoplasm: Specifically, using animal models, it has been demonstrated that soluble tumor antigens within the CNS can reach the CLNs via CSF drainage to stimulate specific T cells.23 Function-blocking antibodies against PD-1 and CTLA-4 have been shown to enhance antitumor T cell responses and resulted in durable antitumor activity in several mouse intracranial tumor models and clinical trials in patients.24–27 However, the response of brain tumors to immunotherapy is relatively weak and survival is still poor, suggesting that more attention should be paid to understand the immunity in brain tumors.