FL9

FL9 (FYAEATPML) is a self-peptide derived from the Fam49b protein that binds to the non-classical MHC class Ib molecule Qa-1b (the murine homolog of HLA-E). Under conditions of cellular stress or defective antigen processing (such as endoplasmic reticulum aminopeptidase associated with antigen processing [ERAAP] deficiency), FL9 is presented on the cell surface of activated CD4+ T cells, particularly follicular helper T (Tfh) cells. This presentation allows recognition and elimination of these pathogenic CD4+ T cells by Qa-1-restricted CD8+ regulatory T cells (CD8 Tregs). FL9 and its engineered superagonist analogs (such as FL9-68) are being developed as peptide vaccines/immunotherapies to mobilize CD8 Tregs, suppress donor-specific antibody (DSA) responses, and prolong graft survival in solid organ transplantation (e.g., heart and kidney allografts) and treat autoimmune diseases like lupus nephritis.

Other names

FL9 peptideFL-9 peptideFL 9 peptideFYAEATPML