White-face hornet venom allergen, Dol m 5.02, is a protein of 204 amino acid residues. This protein and its overlapping fragments, of 53-114 residues in size, containing the N-terminal, middle, and C-terminal regions of the molecule, can be expressed in high yield in bacteria by using the plasmid vector pQE12. Natural (n) and recombinant (r) Dol m 5.02s and the r-fragments are about equally immunogenic for IgG Ab response in BALB/c mice. n-Dol m 5.02 induces mainly murine IgG Abs specific for its discontinuous B cell epitopes and, to a lesser extent, Abs specific for its continuous epitopes. r-Dol m 5.02 and the r-fragments induce only Abs specific for continuous B cell epitopes that are common with those of the n-protein. Abs specific for the discontinuous epitopes show higher affinity than those specific for the continuous epitopes. r-Dol m 5.02 and the r-fragments are as efficient as n-Dol m 5.02 in inducing murine T cell responses specific for the n-protein. The differences in the immunogenicity of n- and r-proteins or r-peptide fragments for B and T cell responses are related to their conformations, inasmuch as only the n-protein is cross-linked by four disulfide bonds. These findings are relevant to the potential use of r-fragments as immunotherapeutic reagents in humans.