Immunologic reactivity in the hypereosinophilic syndrome.

Because previous studies have suggested an important link between eosinophilia and immunologic reactivity, we investigated various components of the immune system in a large number of patients with the idiopathic hypereosinophilic syndrome (HES) to elucidate a possible role for immunologic phenomena in the etiology and pathogenesis of this disease. Immunoglobulin G, A, or M levels were only rarely abnormal. However, in 8 of 21 (38%) patients with HES, IgE levels were markedly elevated suggesting an association of an IgE-mediated mechanism with eosinophilia in this subgroup. Severe dermatographism was present in three fourths of patients, and 2 patients with intermittently elevated histamine levels manifested an unusual form of immediate-pressure urticaria. Serum complement determinations showed elevated C4 and C3 levels in 27% and 77% of patients, respectively. Antigen-antibody complexlike material measured by C1q binding was elevated in the serum of 7 of 22 (32%) patients; this finding may relate to the known ability of eosinophils to avidly phagocytose antigen-antibody complexes. When compared with normals, lymphocytes from patients with HES showed a variety of abnormalities of lymphocyte surface receptors and lymphocyte function. Thus, patients with HES demonstrate a variety of immunologic abnormalities which may be related primarily or secondarily to the pathogenesis of this syndrome.