NRP2 and brain neoplasm: Sensitive methods for the detection of soluble polySia-ESL-1, polySia-NRP2, or even polySia-SynCAM 1 in extracts from brain tissue or in cerebrospinal fluid will allow to determine if shedding of polysialylated proteins by activated microglia, invading monocyte-derived macrophages, and possibly OPCs occurs during acute or chronic neuroinflammation after TBI or other brain insults, in neurogenerative diseases, or in the immune environment of brain tumors.