Analysis of IgG subclasses in chronic active Epstein–Barr virus infection

BACKGROUND: Although elevated serum levels of immunoglobulins are frequently observed in patients with chronic active Epstein-Barr virus (EBV) infection, there have been no reports concerning levels of IgG subclasses. METHODS: Serum levels of IgG subclasses were measured by the enzyme-linked immunosorbent assay (ELISA) in 30 children with severe chronic active EBV infection. RESULTS: Serum levels of IgG1 were elevated in most patients, except for one who showed an abnormally low level of IgG1 and progressive hypogammaglobulinemia. Serum levels of IgG2, IgG3 and IgG4 in the patients were comparable to those in control children, while abnormally low levels of IgG2, IgG3 and IgG4 were observed in six, three and four cases, respectively. CONCLUSION: Although not always susceptible to bacterial infections, low levels of IgG2 were frequently observed in patients with chronic active EBV infection and elevated IgG1 is responsible for the increase of serum IgG in these patients.