FAILURE IN IGA SECRETION BY SURFACE IGA-POSITIVE B-CELLS IN COMMON VARIABLE IMMUNODEFICIENCY (CVID)

CVID is an acquired disease with low serum immunoglobulins. Patients a re classified into three groups on the ability of their B cells to sec rete IgM and IgG in vitro in response to IL-2. We have now extended th is patient classification to include IgA secretion and to assess wheth er the patients have IgA(+) B cells in the circulation. B cells from a lmost all of the CVID patients studied were unable to secrete any IgA in vitro, with or without IL-2, although all B cells tested from norma l donors showed some spontaneous IgA secretion. Thus, the defect with IgA secretion is more profound than with the secretion of IgM or IgG. Despite this failure to secrete IgA, using flow cytometry techniques a ll CVID patients tested were found to have IgA(+) cells (expressed as a percentage of B cells) within the normal range. This suggests that C VID may involve a defect in the secretion of immunoglobulin isotypes r ather than a defect in isotype switching.