FAM19A4 is a secreted, 12 kDa member of the FAM19/TAFA family of chemokine-like proteins. Like other members of the FAM19/TAFA family, with the exception of TAFA5, mature FAM19A4 contains 10 regularly spaced cysteine residues. The FAM19A4 proteins are predominantly expressed in specific regions of the brain and the biological functions of FAM19A4 family members remain to be determined, but there are a few tentative hypotheses. First, FAM19A4 may modulate immune responses in the CNS by functioning as brain specific chemokines, and may act with other chemokines to optimize the recruitment and activity of immune cells in the CNS. Second, FAM19A4 may represent a novel class of neurokines that act as regulators of immune nervous cells. And third, FAM19A4 may control axonal sprouting following brain injury.