Folates play an important role in protein and nucleic acidbiosynthesis and are particularly recognized for their roles in spinal canaland brain development during early pregnancy. FR4 is expressed at high levelson both natural and TGF-b induced Tregs. The majority of CD4+ Tregs express FR4along with CD25 and FoxP3. FR4 antibodies (e.g. clone 12A5 and TH6) recognize asubtype of the receptor (35kD) for the vitamin folic acid also known as folatereceptor d, and folate-binding protein 3. Additionally, there are functionalsimilarities in regulating immune responses between FoxP3 and FR4 expressingCD4+/CD25+ Tregs. CD4+CD25+ FR4hi cells may be used as a functionalimmunosuppressor Treg population which would be expected to express FoxP3.Accordingly, anti-FR4 antibodies may be useful for cell surface staining ofTregs and easy isolation by FACS or magnetic bead separation while maintainingthe cells viability for subsequent down-stream applications.

Key Publication Findings

? FR4 appears to be constitutively expressed in Treg cellsat a higher level than other activated or naive T cells

? Not simply a marker for natural Tregs, but functionallyessential.