Ligand for the receptor complex composed of ilcr-1 and ilcr-2. Binding to the ilcr-1/2 receptor complex triggers a signaling cascade, activating the downsteam signaling components actl-1, pik-1 and nfki-1, and results in increased neuronal activity in RMG interneurons in response to input from oxygen-sensing neurons. This leads to increased animal movement and promotes aggregation behavior. Plays a role in the responsiveness of RMG interneurons to ascaroside pheromones. Homodimer; disulfide-linked. Interacts with the receptor complex composed of ilcr-1 and ilcr-2 with the interaction being mediated by ilcr-2. Expressed in RMG and AUA interneurons and ASE sensory neurons. Belongs to the IL-17 family.