Immunoglobulin‐Secreting Cells in Cord Blood: Effects of Epstein–Barr Virus and Interleukin‐4

The contribution of cord blood B lymphocytes to the immune response has been under considerable investigation. Cord blood B cells produce almost no antibodies except of the immunoglobulin (Ig)M isotype, indicating immaturity of the cells or the environment they reside in. The aim of this study was to investigate the number of circulating IgA‐, IgM‐, IgG‐, and IgE‐producing cells in cord blood in comparison to adult peripheral blood using the ELISPOT method. Moreover, we studied the effect of transformation with the Epstein–Barr virus (EBV) on the proportion of cells producing different isotypes with or without interleukin (IL)‐4. Cord blood had IgM‐producing cells circulating predominantly, but also some IgA‐ and IgG‐producing cells, whereas adult peripheral blood contained high amounts of circulating IgA‐producing cells and some IgM‐ and IgG‐producing cells. No circulating IgE‐producing cells were found in either group. Transformation by EBV caused significant expansion of IgA‐, IgM‐, and IgG‐producing cells in adult peripheral blood, but almost only of IgM‐producing cells in cord blood. A low but detectable expansion of IgA‐ and IgG‐producing cells was found. Cells producing IgE were still not found, even after EBV transformation. However, EBV transformation in the presence of IL‐4 increased the numbers of IgE‐producing cells significantly both in cord blood and adult peripheral blood. These findings indicate that cord blood contains some circulating IgA‐ and IgG‐producing cells that are expanded to some extent after EBV infection. They also indicate that cord blood B cells have a similar capacity for IgE production to adult peripheral blood B cells when appropriately stimulated.