THE GENETICS OF ALLERGY - RFLP ANALYSIS OF HLA AND IMMUNOGLOBULIN HEAVY-CHAIN CONSTANT GENES IN ITALIAN PATIENTS

Fifty-seven atopic, skin-test positive, unrelated Italian patients wit h allergic rhinitis or rhinoconjuntivitis, sensitized to a single alle rgen, were studied. Nine of them showed hypersensitization to grass po llen, thirty-eight were allergic to Urticaceae, nine had positive skin reactivity to mites and one to Betula verrucosa. To investigate the i mmunogenetic components of disease susceptibility, restriction fragmen t length polymorphism (RFLP) analysis of HLA-DR beta, DQ alpha and DO beta genes, and RFLP analysis of switch regions of the immunoglobulin heavy chain constant genes were carried out. Gene frequencies of the a lleles at these loci were not different between patients and Italian c ontrols. Subdividing the patients according to allergen reactivity or to the presence of asthma, HLA frequencies did not show any difference s, whereas the 3.8 Kb fragment at the switch gamma 4 locus was signifi cantly more frequent in patients with allergy to Urticaceae than in th e control population (p = .0087; P-c < .05). Moreover, an increased fr equency of the 4.1 Kb fragment at the same locus was noted in patients with asthma compared to controls (p = .0002; P-c < .01). These result s support: the hypothesis of a multifactorial inheritance of allergy, the Ig heavy chain constant gene region being one of the loci contribu ting to susceptibility (Fund. Clin. Immunol. 4: 35-44, 1996).