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Folates play an important role in protein and nucleic acid biosynthesis and are particularly recognized for their roles in spinal canal and brain development during early pregnancy. FR4 is expressed at high levels on both natural and TGF-b induced Tregs. The majority of CD4+ Tregs express FR4 along with CD25 and FoxP3. FR4 antibodies (e.g. clone 12A5 and TH6) recognize a subtype of the receptor (35kD) for the vitamin folic acid also known as folate receptor d, and folate-binding protein 3. Additionally, there are functional similarities in regulating immune responses between FoxP3 and FR4 expressing CD4+/CD25+ Tregs. CD4+CD25+ FR4hi cells may be used as a functional immunosuppressor Treg population which would be expected to express FoxP3. Accordingly, anti-FR4 antibodies may be useful for cell surface staining of Tregs and easy isolation by FACS or magnetic bead separation while maintaining the cells viability for subsequent down-stream applications.
Key Publication Findings
• FR4 appears to be constitutively expressed in Treg cells at a higher level than other activated or naive T cells
• Not simply a marker for natural Tregs, but functionally essential
Key Publication
Yamaguchi T et al. 2007. Immunity. 27:145-159
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FIGURE 1. Tri-color staining of BALB/c splenocytes for FR4 FITC (12A5), CD4 PE (BD) and CD25 APC (Imgenex). CD4+CD25+; CD4+CD25- and CD4- cells were analyzed for FR4 expressing respective histograms by flow cytometry. Appropriate isotype control was used. |
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FIGURE 2. Tri-color staining of BALB/c splenocytes for FR4 FITC (IMG-6217C and IMG-6218C used at 0.06 ug/10^6 cells), CD4 PE (IMG-5922D) and CD25 APC (IMG-5924G). CD4+CD25+, CD4+CD25-, and CD4- cells were analyzed for CD4 and FR4 expression by dot-plot flow cytometry. Appropriate isotype control was used.
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FIGURE 3. Flow cytometric analysis of intracellular FOXP3 (IMG-5802D) and cell surface FR4 with clone 12A5 (IMG-6217C) (left) and clone TH6 (IMG-6218C) (right) at 0.06 ug/10^6 mouse splenocytes. | | |
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