Soluble Fc epsilon R II levels in normal children and patients with immunodeficiency diseases.

CD23 is expressed on mature B cells and is identical to a low-affinity IgE Fc epsilon receptor type II (Fc epsilon R II). The C terminal portion of CD23 is released to the serum as soluble Fc epsilon R II (sFc epsilon R II), which may be involved in regulation of IgE synthesis. We studied sFc epsilon R II levels in normal children and in patients with immunodeficiencies, including common variable immunodeficiency (CVI), partial DiGeorge syndrome, and immunodeficiency associated with ectodermal dysplasia to examine the relationship of sFc epsilon R II levels to B cell numbers and other immunoparameters. Serum Fc epsilon R II levels are higher in younger children (younger than 3 years) and decline gradually with age. In 11 patients with CVI with normal numbers of B cells (greater than 6%), sFc epsilon R II levels were comparable to that of control subjects. Five patients with CVI with deficiencies of peripheral B cells had levels of sFc epsilon R II similar to levels of control subjects. In all but one patient with partial DiGeorge syndrome, sFc epsilon R II levels were not significantly elevated, despite the presence of elevated peripheral B cell numbers. Of six patients with ectodermal dysplasia, four demonstrated increased Fc epsilon R II levels, a finding not correlated with serum IgE levels or with peripheral eosinophil or B cell numbers.