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FOXP3 is a master regulator of immune homeostasis expressed specifically in CD4+ CD25+ T regulatory cells controlling their growth, development and function and generally accepted to be expressed in both mouse and human CD4+ CD25+ regulatory T cells. Whereas mouse is detected as a single band in WB studies, human FOXP3 is consistently seen as a doublet. The lower band has been identified as a splice isoform lacking exon 2 with a predicted molecular weight of ~4 kDa less than FOXP3. Transient transfection assays using Jurkat cells suggest that the FOXP3D2 is a novel splice variant that functions as a transcriptional repressor protein and acts in cohort with FOXP3 causing a significant suppression of cytokines and up-regulating the expression of various Treg-associated markers. The existence of functional splice variant forms of FOXP3 suggest an additional level of complexity related to it's biology, although the significance of FOXP3 splice variant forms remains to be elucidated. |
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Western blot analysis of FOXP3D2 and full-length (wild-type) transfected 293 cell lysate using IMG-6018 and IMG-5802A. IMG-6018 specifically detects the FOXP3D2 (Lane 1); it does not detect full-length FOXP3 (Lane 2). In contrast, IMG-5802A detects both FOXP3D2 (Lane 3) and full-length (Lane 4) FOXP3. | | | |