Decreased cytoplasmic immunoglobulin A production during Epstein-Barr virus immortalization on lymphocytes from patients with ataxia-telangiectasia.

Previously, we have reported significantly lower immunoglobulin (Ig) A production in supernatants of cultured lymphoblastoid cells using enzyme-linked immunosorbent assay from patients with ataxia-telangiectasia (AT) when compared to that of age- and sex-matched healthy individuals. Here, we further assess the degree of cytoplasmic Ig production in these cells and also analyze it during the early phase of Epstein-Barr virus immortalization. All classes of cytoplasmic IgM, IgG, and IgA productions were demonstrated in cells from healthy controls. In contrast, cells from patients with AT showed only cytoplasmic IgM and IgG with low or nondetectable levels of IgA during and after the immortalizing process. These results suggest B lymphocytes bearing IgA are functionally immature and/or defective in patients with AT.