TAFA4/FAM19A4: ProductsTAFA4 (also FAM19A4) is a secreted, 12 kDa member of the FAM19/TAFA family of chemokine-like proteins (1). It is synthesized as a 140 amino acid (aa) precursor that contains a 35 aa signal sequence and a 105 aa mature chain (SwissProt #: Q8N3H0). Like other members of the FAM19/TAFA family, with the exception of TAFA5, mature TAFA1 contains 10 regularly spaced cysteine residues that follow the pattern CX7CCX13CXCX14CX11CX4CX5CX10C, where C represents a conserved cysteine residue and X represents any noncysteine amino acid. Human TAFA4 is 90% aa identical to mouse TAFA4. Real-time PCR analysis indicates that TAFA4 mRNA expression is restricted to the central nervous system (CNS), with the highest level in the thalamus. The biological functions of TAFA family members remain to be determined, but there are a few tentative hypotheses. First, TAFAs 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, TAFAs may represent a novel class of neurokines that act as regulators of immune nervous cells. And third, TAFAs may control axonal sprouting following brain injury.