Overall approach to the creation of NIGO. The creation of NIGO was done in two main stages: 1. Clipping by relevance to specific organisms. Terms that are not used to annotate genes or gene products in human, rat or mouse (according to the GOA-EBI annotation files) were removed while higher classes of terms kept were also kept to preserve the consistency of the graph. 2. Manually clipping according to biological relevance of the GO terms to the neural/immune systems. A total number of 22,002 terms were deleted from the full GO in order to create NIGO.