965 REGULATION OF IgA SUBCLASS PRODUCTION BY EPSTEIN BARR VIRUS

Abstract

We have demonstrated by limiting dilution analysis that a high percentage of clones derived from Epstein-Barr Virus (EBV) stimulated peripheral blood lymphocytes (PBL) secrete IgA. To further characterize the IgA produced by these clones the IgA subclass of supernatants from clones stimulated 6–8 weeks earlier with EBV was determined by RIA. 17/17 clones were positive for IgA1; none were positive for lgA2. Because we have shown an enrichment for lgA2 precursors in surface lgM+ B cells, panning techniques were used to separate slgM+ B cells from tonsils. 32/32 clones from these slgM+ B cells secreted IgA1, none secreted lgA2. Past experiments have demonstrated a discordance between plasma cell production and immunoglobulin secretion. Therefore cytoplasmic staining for lgA2 was done on EBV stimulated PBL harvested 7, 10, 14 and 21 days after culture. In all 5 experiments, the percentage of IgA plasma cells positive for IgA2 decreased with increasing duration of culture. A mean of 25.5% of the IgA plasma cells were positive for lgA2 at Day 7 and 7.2% at Day 21. These results are unlikely to be due to isotype switching from lgA2 to IgA1 as the gene for α2 is more distal to the gene than the gene for α1. Instead, there may be a difference between limited proliferation and differentiation induced by EBV, and immortalization. Although lgA2 plasma cell precursors may undergo some proliferation and differentiation after EBV stimulation they are not immortalized. There is selective immortalization of lgA1 producing cells.