G4 peptide (SIIGFEKL) is a variant of the agonist ovalbumin (OVA) peptide (257-264), SIINFEKL. OVA Peptide is a class I (Kb)-restricted peptide epitope of ovalbumin presented by the class I MHC (major histocompatibility complex) molecule, H-2Kb (class I genes of the mouse MHC).