IgE, CD8+CD60+ T Cells and IFN-α in Human Immunity to Parvovirus B19 in Selective IgA Deficiency

Although IgE is implicated in viral immunity, its role in parvovirus B19 immunity and its relationship to other immunological states has not been studied. Total serum immunoglobulin levels, IgG and IgE anti-parvovirus B19, blood lymphocyte numbers, and epsilon and cytokine specific mRNA were determined in pediatric patients with normal serum IgA levels (IgA+) and selective IgA deficiency (IgA−) on days 0 (initial diagnosis) and 14, and 3 years after recovery (nephelometry, Western blot test, flow cytometry, reverse transcriptase-polymerase chain reaction). We found that both patients had serum IgM, IgG, IgE, and IgA levels within normal ranges on day 0 to 3 years, excluding IgG1 and IgA in the IgA− patient, which were elevated and negative, respectively, and IgE in the IgA+ patient, which was elevated (>100 IU/ml). The serum IgA+ and IgA− patients made IgE (and IgG) anti-parvovirus B19 at all time points. Excluding CD8+CD60+ T cells, determinations of T, B, and NK lymphocyte subsets always were within normal ranges. In both patients, CD8+CD60+ T-cell numbers were within normal ranges on day 0, but dramatically increased on day 14 (more than fivefold). At 3 years, they had returned to normal in the IgA+ patient, but remained high in the IgA− patient. On day 0 to 3 years, peripheral blood mononuclear cells of both patients expressed epsilon- and interferon (IFN)-α-specific mRNA. On day 0, the IgA+ patient expressed interleukin (IL)-4 and IL-10, but not IL-2, IFN-γ, or IL-6 mRNA; the IgA− patient expressed IL-6 and IL-10 mRNA, but not IL-4, IL-2, or IFN-γ mRNA. At 3 years, the IgA+ patient expressed mRNA for all cytokines, but the IgA− patient did not express mRNA for any of these cytokines. Our results suggest that IgE is important in parvovirus B19 immunity, and that IFN-α and CD8+CD60+ T cells may regulate IgE memory responses and isotype switching.