DNA molecule (I) corresponding to sequences (SEQ ID. No. 1), (SEQ ID. No. 3) and (SEQ ID. No. 5), all of 1503 bp (defined in the specification) are new. Independent claims are also included for the following: (1) DNA (Ia) comprising a sequence of (I) beginning at position 70 and encoding a polypeptide (II) with the properties of the major allergen Phl p4 of Phleum pratense； (2) DNA (Ib) corresponding to a sequence that encodes Phl p4； (3) DNA (Ic) that hybridizes to (I), (Ia) or (Ib) under stringent conditions and is derived from Poaceae； (4) DNA (Id) encoding a polypeptide (IIa) immunologically cross-reactive with Phl p4 and derived from Poaceae； (5) DNA (Ie) containing a fragment, or combination of fragments, of (I)-(Id) and encoding an immunomodulatory, T cell-reactive form of a Group 4 Poaceae allergen； (6) any of (I)-(Ie) encoding an immunomodulatory T cell-reactive fragment that is altered by targeted mutation of an individual codon, elimination or addition； (7) recombinant DNA expression vector, or cloning system, containing any of (I)-(Ie), or the mutants of (6), linked to expression control sequences； (8) host organism transformed with any of the new DNAs or the vector of (7)； (9) method for preparing a polypeptide by culturing the hosts of (8)； and (10) polypeptides (IIb) encoded by any of (I)-(Ie) or the mutants of (6). ACTIVITY : Antiallergic. No details of tests for antiallergic activity are given. MECHANISM OF ACTION : Vaccine； hyposensitization.
