Atopic asthma is dominant in elderly onset asthmatics: Possibility for an alteration of mast cell function by aging through Fc receptor expression

The morbidity and mortality of elderly onset asthma have recently been on t he increase. To evaluate the allergic status of the elderly onset asthmatic s, we performed skin tests for allergens and estimated serum total IgE leve ls of the patients. The proportion of the skin-test-positive patients among the elderly onset asthmatics was significantly larger than that in the you nger onset group, whereas no significant difference was observed in the fre quency of patients with serum total IgE levels higher than the normal range (287.2 IU/ml). On the other hand, in the experiments with aged mice, isola ted peritoneal mast cells (PMC) showed a considerable decrease in the Fc ga mma RIIB/III expression and higher degranulation triggered by 2.4G2, as com pared to the PMC derived from young mice. Since FcyRIIB has been shown to a ct as a negative regulator, we speculate that in the aged mice Fc receptor- mediated mast cell function may be upregulated by a release from the negati ve regulation as a result of decreased Fc gamma RIIB expression. Our result s obtained from a mouse model system may help to understand pathophysiologi cal mechanisms underlying elderly onset asthma.