Screening of a Parietaria pollen- lambda gt22 library with antisera to a 14-kDa pollen protein from Parietaria led to the identification of several cDNA clones encoding allergenic proteins. Nucleotide sequence analysis of these clones indicated that, on the basis of the sequence homologies, these clones may be classified to three groups; group I (PJ001) comprising seven isoallergens, group II (PJ002) comprising two isoallergens and group III (PJ003) with three isoallergenic variants. Four of these cDNAs were expressed in pCNAII vectors which bound to the murine antibodies. IgE binding assay with 15-residue peptides designed from the deduced sequences of one of the group I proteins revealed a dominant IgE-binding region which spanned two overlapping peptides, peptides #27 and #28. These peptides are conserved among all of the group I iso-allergens.; Furthermore, a murine monoclonal antibody directed to a major Parietaria- allergen bound to peptide #28, suggesting that this peptide is recognized by mouse antibodies as well. In a splenocyte culture of mice immunized with Parietaria allergens, peptide #28 stimulated the production cytokines IL-2, IL-4 and IFN- gamma , whereas, peptide #23 stimulated production of only cytokine IFN- gamma . Furthermore, Parietaria-specific antibodies were found in sera of North American subjects and these antibodies were shown to bind the 14 kDa Par j I allergen. Accordingly, these recombinant Parietaria allergens are useful in both diagnosis and therapy of allergic diseases induced by Parietaria pollens.